def bind(self, frame):
if not self.ui.get_widget('/MenuBar/ViewMenu/ShowBonds'
).get_active():
self.bonds = np.empty((0, 5), int)
return
from ase.atoms import Atoms
from ase.neighborlist import NeighborList
nl = NeighborList(self.images.r * 1.5, skin=0, self_interaction=False)
nl.update(Atoms(positions=self.images.P[frame],
cell=(self.images.repeat[:, np.newaxis] *
self.images.A[frame]),
pbc=self.images.pbc))
nb = nl.nneighbors + nl.npbcneighbors
self.bonds = np.empty((nb, 5), int)
self.coordination = np.zeros((self.images.natoms), dtype=int)
if nb == 0:
return
n1 = 0
for a in range(self.images.natoms):
indices, offsets = nl.get_neighbors(a)
self.coordination[a] += len(indices)
for a2 in indices:
self.coordination[a2] += 1
n2 = n1 + len(indices)
self.bonds[n1:n2, 0] = a
self.bonds[n1:n2, 1] = indices
self.bonds[n1:n2, 2:] = offsets
n1 = n2
i = self.bonds[:n2, 2:].any(1)
self.bonds[n2:, 0] = self.bonds[i, 1]
self.bonds[n2:, 1] = self.bonds[i, 0]
self.bonds[n2:, 2:] = -self.bonds[i, 2:]
def candidates_combos(atoms, edge=None, pore_size=None):
"""Return candidate pore indices combinations."""
from itertools import combinations
cans = []
indices = [a.index for a in atoms if a.index not in edge]
nblist = NeighborList([graphene_cutoff for i in range(len(atoms))],
bothways=True,
self_interaction=False)
nblist.update(atoms)
def constraint_check(pores):
for pore in pores:
remains = [a.index for a in atoms if a.index not in pore]
if is_connected(nblist, remains) and is_connected(nblist, pore):
cans.append(pore)
if pore_size is not None:
pores = combinations(indices, pore_size)
print(sum([1 for p in pores]))
pores = combinations(indices, pore_size)
constraint_check(pores)
else:
for i in range(1, len(indices)):
pores = combinations(indices, i)
constraint_check(pores)
return cans
def get_bondpairs(atoms, radius=1.1):
"""Get all pairs of bonding atoms
Return all pairs of atoms which are closer than radius times the
sum of their respective covalent radii. The pairs are returned as
tuples::
(a, b, (i1, i2, i3))
so that atoms a bonds to atom b displaced by the vector::
_ _ _
i c + i c + i c ,
1 1 2 2 3 3
where c1, c2 and c3 are the unit cell vectors and i1, i2, i3 are
integers."""
from ase.data import covalent_radii
from ase.neighborlist import NeighborList
cutoffs = radius * covalent_radii[atoms.numbers]
nl = NeighborList(cutoffs=cutoffs, self_interaction=False)
nl.update(atoms)
bondpairs = []
for a in range(len(atoms)):
indices, offsets = nl.get_neighbors(a)
bondpairs.extend([(a, a2, offset)
for a2, offset in zip(indices, offsets)])
return bondpairs
def is_connected(reference, indices, cutoff=graphene_cutoff):
"""Return True if indices in atoms are connected.
Args:
reference (Atoms or NeighborList): Structure containing atoms for test. The NeighborList must be constructed with bothways=True.
indices (List[int]): Indices of the possibly connected atoms.
cutoff (int): Radius defining neighbors in a NeighborList. Only relevent when reference is of the Atoms type.
"""
if isinstance(reference, Atoms):
nblist = NeighborList([cutoff for i in range(len(reference))],
bothways=True,
self_interaction=False)
nblist.update(reference)
else:
nblist = reference
if len(indices) == 0:
return True
connected = [indices[0]]
for c in connected:
neighbs = nblist.get_neighbors(c)[0]
for n in neighbs:
if n in indices and n not in connected:
connected.append(n)
return set(indices) == set(connected)
def randomize_biatom_13(atoms, type_a, type_b, ratio):
""" replace randomly by clusters of 13 atoms
to acheive target conc """
n_A = 0
n_B = 0
for atom in atoms:
if atom.symbol == type_a:
n_A += 1
elif atom.symbol == type_b:
n_B += 1
else:
raise Exception('Extra chemical element %s!'%atom.symbol)
#print n_A, n_B
N = len(atoms)
nl = NeighborList([1.5]*N, self_interaction=False, bothways=True) # 2*1.5=3 Angstr. radius
nl.build(atoms)
#print "conc", n_A *1.0 / N
r = random.Random()
while n_A < ratio*N: # add A atoms randomly
index = r.randint(0, N-1)
if (atoms[index].symbol != type_a):
#print "changing atom #"+str(index)+" to "+type_a
#if (r.randint(0, 1000) < 500):
atoms[index].symbol = type_a
n_A += 1
indeces, offsets = nl.get_neighbors(index)
for ia in indeces :
if (atoms[ia].symbol != type_a)&(n_A < ratio*N):
atoms[ia].symbol = type_a
n_A += 1
return atoms
def get_bonds(atoms, covalent_radii):
from ase.neighborlist import NeighborList
nl = NeighborList(covalent_radii * 1.5,
skin=0, self_interaction=False)
nl.update(atoms)
nbonds = nl.nneighbors + nl.npbcneighbors
bonds = np.empty((nbonds, 5), int)
if nbonds == 0:
return bonds
n1 = 0
for a in range(len(atoms)):
indices, offsets = nl.get_neighbors(a)
n2 = n1 + len(indices)
bonds[n1:n2, 0] = a
bonds[n1:n2, 1] = indices
bonds[n1:n2, 2:] = offsets
n1 = n2
i = bonds[:n2, 2:].any(1)
pbcbonds = bonds[:n2][i]
bonds[n2:, 0] = pbcbonds[:, 1]
bonds[n2:, 1] = pbcbonds[:, 0]
bonds[n2:, 2:] = -pbcbonds[:, 2:]
return bonds
def exafs_first_shell(S02, energy_shift, absorber,
ignore_elements, edge, neighbor_cutoff, trajectory):
feff_options = {
'RMAX':str(neighbor_cutoff),
'HOLE':'%i %.4f' % (feff_edge_number(edge), S02),
'CORRECTIONS':'%.4f %.4f' % (energy_shift, 0.0),
}
#get the bulk reference state
path = exafs_reference_path(absorber, feff_options)
k = None
chi_total = None
counter = -1
interactions = 0
nl = None
for step, atoms in enumerate(trajectory):
if COMM_WORLD.rank == 0:
time_stamp = strftime("%F %T")
print '[%s] step %i/%i' % (time_stamp, step+1, len(trajectory))
atoms = atoms.copy()
if ignore_elements:
ignore_indicies = [atom.index for atom in atoms
if atom.symbol in ignore_elements]
del atoms[ignore_indicies]
if nl is None:
nl = NeighborList(len(atoms)*[neighbor_cutoff], skin=0.3,
self_interaction=False)
nl.update(atoms)
for i in xrange(len(atoms)):
if atoms[i].symbol != absorber:
continue
indicies, offsets = nl.get_neighbors(i)
for j, offset in zip(indicies, offsets):
counter += 1
if counter % COMM_WORLD.size != COMM_WORLD.rank:
continue
r = atoms.get_distance(i,j,True)
if r >= neighbor_cutoff: continue
interactions += 1
k, chi = chi_path(path, r, 0.0, energy_shift, S02, 1)
if chi_total is not None:
chi_total += chi
else:
chi_total = chi
chi_total = COMM_WORLD.allreduce(chi_total)
chi_total /= atoms.get_chemical_symbols().count(absorber)
chi_total /= len(trajectory)
chi_total *= 2
return k, chi_total
def update(self, atoms):
# check all the elements are available in the potential
self.Nelements = len(self.elements)
elements = np.unique(atoms.get_chemical_symbols())
unavailable = np.logical_not(
np.array([item in self.elements for item in elements]))
if np.any(unavailable):
raise RuntimeError('These elements are not in the potential: %s' %
elements[unavailable])
# cutoffs need to be a vector for NeighborList
cutoffs = self.cutoff * np.ones(len(atoms))
# convert the elements to an index of the position
# in the eam format
self.index = np.array([self.elements.index(el)
for el in atoms.get_chemical_symbols()])
self.pbc = atoms.get_pbc()
# since we need the contribution of all neighbors to the
# local electron density we cannot just calculate and use
# one way neighbors
self.neighbors = NeighborList(cutoffs,
skin=self.parameters.skin,
self_interaction=False,
bothways=True)
self.neighbors.update(atoms)
def initialize(self, atoms):
self.par = {}
self.rc = 0.0
self.numbers = atoms.get_atomic_numbers()
if self.parameters.asap_cutoff:
relevant_pars = {}
for symb, p in parameters.items():
if atomic_numbers[symb] in self.numbers:
relevant_pars[symb] = p
else:
relevant_pars = parameters
maxseq = max(par[1] for par in relevant_pars.values()) * Bohr
rc = self.rc = beta * maxseq * 0.5 * (sqrt(3) + sqrt(4))
rr = rc * 2 * sqrt(4) / (sqrt(3) + sqrt(4))
self.acut = np.log(9999.0) / (rr - rc)
if self.parameters.asap_cutoff:
self.rc_list = self.rc * 1.045
else:
self.rc_list = self.rc + 0.5
for Z in self.numbers:
if Z not in self.par:
p = parameters[chemical_symbols[Z]]
s0 = p[1] * Bohr
eta2 = p[3] / Bohr
kappa = p[4] / Bohr
x = eta2 * beta * s0
gamma1 = 0.0
gamma2 = 0.0
for i, n in enumerate([12, 6, 24]):
r = s0 * beta * sqrt(i + 1)
x = n / (12 * (1.0 + exp(self.acut * (r - rc))))
gamma1 += x * exp(-eta2 * (r - beta * s0))
gamma2 += x * exp(-kappa / beta * (r - beta * s0))
self.par[Z] = {'E0': p[0],
's0': s0,
'V0': p[2],
'eta2': eta2,
'kappa': kappa,
'lambda': p[5] / Bohr,
'n0': p[6] / Bohr**3,
'rc': rc,
'gamma1': gamma1,
'gamma2': gamma2}
self.ksi = {}
for s1, p1 in self.par.items():
self.ksi[s1] = {}
for s2, p2 in self.par.items():
self.ksi[s1][s2] = p2['n0'] / p1['n0']
self.forces = np.empty((len(atoms), 3))
self.sigma1 = np.empty(len(atoms))
self.deds = np.empty(len(atoms))
self.nl = NeighborList([0.5 * self.rc_list] * len(atoms),
self_interaction=False)
def hop_shuffle(atoms, A, B, count=10, R=3.0):
"""
Shuffle atoms in given structure
by swapping atom types within first coordination shell
Parameters
----------
atoms: ase.Atoms
ase Atoms object, containing atomic cluster.
A, B: string
symbols of atoms to swap
count: integer
number of shuffles
R: float
radius of coordination shell, were atoms will be swapped
Returns
-------
Function returns ASE atoms object whith
shuffled atoms
"""
n_atoms = len(atoms)
nswaps = 0
neiblist = NeighborList( [ R ] * n_atoms,
self_interaction=False,
bothways=True )
neiblist.build( atoms )
rnd = random.Random()
while nswaps < count:
i = rnd.randint(0, n_atoms-1)
indeces, offsets = neiblist.get_neighbors( i )
if (atoms[i].symbol == B):
candidates = []
for ii in indeces:
if atoms[ii].symbol == A:
candidates.append( ii )
if len(candidates) > 0:
j = random.choice(candidates)
atoms[i].symbol = A
atoms[j].symbol = B
nswaps += 1
neiblist.build( atoms )
elif (atoms[i].symbol == B):
candidates = []
for ii in indeces:
if atoms[ii].symbol == A:
candidates.append( ii )
if len(candidates) > 0:
j = random.choice(candidates)
atoms[i].symbol = B
atoms[j].symbol = A
nswaps += 1
neiblist.build( atoms )
return atoms
def calculate(self, atoms=None,
properties=['energy'],
system_changes=all_changes):
Calculator.calculate(self, atoms, properties, system_changes)
natoms = len(self.atoms)
sigma = self.parameters.sigma
epsilon = self.parameters.epsilon
rc = self.parameters.rc
if rc is None:
rc = 3 * sigma
if 'numbers' in system_changes:
self.nl = NeighborList([rc / 2] * natoms, self_interaction=False)
self.nl.update(self.atoms)
positions = self.atoms.positions
cell = self.atoms.cell
e0 = 4 * epsilon * ((sigma / rc)**12 - (sigma / rc)**6)
energy = 0.0
forces = np.zeros((natoms, 3))
stress = np.zeros((3, 3))
for a1 in range(natoms):
neighbors, offsets = self.nl.get_neighbors(a1)
cells = np.dot(offsets, cell)
d = positions[neighbors] + cells - positions[a1]
r2 = (d**2).sum(1)
c6 = (sigma**2 / r2)**3
c6[r2 > rc**2] = 0.0
energy -= e0 * (c6 != 0.0).sum()
c12 = c6**2
energy += 4 * epsilon * (c12 - c6).sum()
f = (24 * epsilon * (2 * c12 - c6) / r2)[:, np.newaxis] * d
forces[a1] -= f.sum(axis=0)
for a2, f2 in zip(neighbors, f):
forces[a2] += f2
stress += np.dot(f.T, d)
if 'stress' in properties:
if self.atoms.number_of_lattice_vectors == 3:
stress += stress.T.copy()
stress *= -0.5 / self.atoms.get_volume()
self.results['stress'] = stress.flat[[0, 4, 8, 5, 2, 1]]
else:
raise PropertyNotImplementedError
self.results['energy'] = energy
self.results['free_energy'] = energy
self.results['forces'] = forces
class TwoCenterHoppingIntegrals:
def __init__(self, bopatoms: BOPAtoms, cutoffs: list, **kwargs):
self.bopatoms = bopatoms
self.nl = NeighborList(cutoffs=cutoffs, bothways=True, self_interaction=False, **kwargs)
self.nl.update(bopatoms)
def update_hops(self):
raise NotImplemented
def get_single_hop_global(self, atomindex: int, jneigh: int):
hop = self.get_single_hop_local(atomindex, jneigh)
rot = self.get_rotation(atomindex, jneigh)
return hop
def get_single_hop_local(self, atomindex: int, jneigh: int):
bopatom_i = self.bopatoms[atomindex]
(bopatom_neighbors_i, scaled_pos_list) = self.nl.get_neighbors(atomindex)
bopatom_j_neigh_i = self.bopatoms[bopatom_neighbors_i[jneigh]]
pos_list = np.dot(scaled_pos_list, self.bopatoms.get_cell())
rel_pos_ij = pos_list[jneigh]
r_ij = np.linalg.norm(rel_pos_ij)
ss_sigma = 0
sp_sigma = 0
sd_sigma = 0
pp_sigma = 0
pp_pi = 0
pd_sigma = 0
pd_pi = 0
dd_sigma = 0
dd_pi = 0
dd_delta = 0
slater_koster_matrix = np.zeros((9, 9))
# initialize bond integrals
if bopatom_i.number_valence_orbitals == 5 and bopatom_j_neigh_i.number_valence_orbitals == 5:
dd_sigma = np.exp(-r_ij * 1)
dd_pi = np.exp(-r_ij * 2)
dd_delta = np.exp(-r_ij * 3)
slater_koster_matrix[4, 4] = dd_delta
slater_koster_matrix[5, 5] = dd_pi
slater_koster_matrix[6, 6] = dd_pi
slater_koster_matrix[7, 7] = dd_delta
slater_koster_matrix[8, 8] = dd_sigma
return slater_koster_matrix[4:, 4:]
def get_relative_position(self, index: int, jneigh: int):
'''
:param index: atom index
:param jneigh: indexing neighboring atoms of atom index
:return:
'''
# if index > len(self.bopatoms):
# raise IndexError
# if jneigh > self.nl.nneighbors - 1:
# raise IndexError
(index_list, relative_position_list) = self.nl.get_neighbors(index)
return relative_position_list[jneigh]
def get_rotation(self, atomindex: int, jneigh:int, z_axis_global: np.array=np.array([0, 0, 1])) -> Rotation:
rel_pos = self.get_relative_position(atomindex, jneigh)
v = np.cross(rel_pos, z_axis_global)
cosine = np.dot(rel_pos, z_axis_global)
if cosine != -1:
v_cross = [[0 , -v[2], v[1] ],
[v[2] , 0 , -v[0]],
[-v[1], v[0] , 0]]
rotation_matrix = np.eye(3) + v_cross + np.dot(v_cross, v_cross) / (1 + cosine)
else:
rotation_matrix = np.diag([1, 1, -1])
return Rotation.from_dcm(rotation_matrix)
def get_dbond_rotation_matrix(self, theta: float, phi: float):
'''
assumes bond to be ordered in ddsigma, ddpi, ddpi, dddelta
:param theta:
:param phi:
:return:
'''
from numpy import sqrt, cos, sin
rot = np.zeros((5,5))
rot[4, 3] = -2 * sin(phi) * cos(phi) * cos(theta)
rot[3, 3] = cos(phi)**2 - sin(phi)**2
rot[2, 3] = -2 * sin(phi) * cos(phi) * sin(theta)
rot[1, 3] = (cos(phi)**2 - sin(phi)**2) * sin(theta) * cos(theta)
rot[0, 3] = (cos(phi)**2 - sin(phi)**2) * sqrt(3/4.) * sin(theta)**2
rot[4, 1] = sin(phi) * sin(theta)
rot[3, 1] = -cos(phi) * sin(theta) * cos(theta)
rot[2, 1] = -sin(phi) * cos(theta)
rot[1, 1] = cos(phi) * (cos(phi)**2 - sin(phi)**2)
rot[0, 1] = sqrt(3) * cos(phi) * sin(theta) * cos(theta)
rot[4, 0] = 0
rot[3, 0] = sqrt(3/4.) * sin(theta)**2
rot[2, 0] = 0
rot[1, 0] = -sqrt(3) * sin(theta) * cos(theta)
rot[0, 0] = cos(theta)**2 - 0.5 * sin(theta)**2
rot[4, 2] = -cos(phi) * sin(theta)
rot[3, 2] = -sin(phi) * sin(theta) * cos(theta)
rot[2, 2] = cos(phi) * cos(theta)
rot[1, 2] = sin(phi) * (cos(theta)**2 - sin(theta)**2)
rot[0, 2] = sqrt(3) * sin(phi) * sin(theta) * cos(theta)
rot[4, 4] = (cos(phi)**2 - sin(phi)**2) * cos(theta)
rot[3, 4] = sin(phi) * cos(phi) * (cos(theta)**2 + 1)
rot[2, 4] = (cos(phi)**2 - sin(phi)**2) * sin(theta)
rot[1, 4] = 2 * sin(phi) * cos(phi) * sin(theta) * cos(theta)
rot[0, 4] = sqrt(3) * sin(phi) * cos(phi) * sin(theta)**2
return rot
def _take_fingerprints(self, atoms, individual=False):
""" Returns a [fingerprints,typedic] list, where fingerprints
is a dictionary with the fingerprints, and typedic is a
dictionary with the list of atom indices for each element
(or "type") in the atoms object.
The keys in the fingerprints dictionary are the (A,B) tuples,
which are the different element-element combinations in the
atoms object (A and B are the atomic numbers).
When A != B, the (A,B) tuple is sorted (A < B).
If individual=True, a dict is returned, where each atom index
has an {atomic_number:fingerprint} dict as value.
If individual=False, the fingerprints from atoms of the same
atomic number are added together."""
pos = atoms.get_positions()
num = atoms.get_atomic_numbers()
cell = atoms.get_cell()
unique_types = np.unique(num)
posdic = {}
typedic = {}
for t in unique_types:
tlist = [i for i, atom in enumerate(atoms) if atom.number == t]
typedic[t] = tlist
posdic[t] = pos[tlist]
# determining the volume normalization and other parameters
volume, pmin, pmax, qmin, qmax = self._get_volume(atoms)
# functions for calculating the surface area
non_pbc_dirs = [i for i in range(3) if not self.pbc[i]]
def surface_area_0d(r):
return 4 * np.pi * (r**2)
def surface_area_1d(r, pos):
q0 = pos[non_pbc_dirs[1]]
phi1 = np.lib.scimath.arccos((qmax - q0) / r).real
phi2 = np.pi - np.lib.scimath.arccos((qmin - q0) / r).real
factor = 1 - (phi1 + phi2) / np.pi
return surface_area_2d(r, pos) * factor
def surface_area_2d(r, pos):
p0 = pos[non_pbc_dirs[0]]
area = np.minimum(pmax - p0, r) + np.minimum(p0 - pmin, r)
area *= 2 * np.pi * r
return area
def surface_area_3d(r):
return 4 * np.pi * (r**2)
# build neighborlist
# this is computationally the most intensive part
a = atoms.copy()
a.set_pbc(self.pbc)
nl = NeighborList([self.rcut / 2.] * len(a),
skin=0.,
self_interaction=False,
bothways=True)
nl.update(a)
# parameters for the binning:
m = int(np.ceil(self.nsigma * self.sigma / self.binwidth))
x = 0.25 * np.sqrt(2) * self.binwidth * (2 * m + 1) * 1. / self.sigma
smearing_norm = erf(x)
nbins = int(np.ceil(self.rcut * 1. / self.binwidth))
bindist = self.binwidth * np.arange(1, nbins + 1)
def take_individual_rdf(index, unique_type):
# Computes the radial distribution function of atoms
# of type unique_type around the atom with index "index".
rdf = np.zeros(nbins)
if self.dimensions == 3:
weights = 1. / surface_area_3d(bindist)
elif self.dimensions == 2:
weights = 1. / surface_area_2d(bindist, pos[index])
elif self.dimensions == 1:
weights = 1. / surface_area_1d(bindist, pos[index])
elif self.dimensions == 0:
weights = 1. / surface_area_0d(bindist)
weights /= self.binwidth
indices, offsets = nl.get_neighbors(index)
valid = np.where(num[indices] == unique_type)
p = pos[indices[valid]] + np.dot(offsets[valid], cell)
r = cdist(p, [pos[index]])
bins = np.floor(r / self.binwidth)
for i in range(-m, m + 1):
newbins = bins + i
valid = np.where((newbins >= 0) & (newbins < nbins))
valid_bins = newbins[valid].astype(int)
values = weights[valid_bins]
c = 0.25 * np.sqrt(2) * self.binwidth * 1. / self.sigma
values *= 0.5 * erf(c * (2 * i + 1)) - \
0.5 * erf(c * (2 * i - 1))
values /= smearing_norm
for j, valid_bin in enumerate(valid_bins):
rdf[valid_bin] += values[j]
rdf /= len(typedic[unique_type]) * 1. / volume
return rdf
fingerprints = {}
if individual:
for i in range(len(atoms)):
fingerprints[i] = {}
for unique_type in unique_types:
fingerprint = take_individual_rdf(i, unique_type)
if self.dimensions > 0:
fingerprint -= 1
fingerprints[i][unique_type] = fingerprint
else:
for t1, t2 in combinations_with_replacement(unique_types, r=2):
key = (t1, t2)
fingerprint = np.zeros(nbins)
for i in typedic[t1]:
fingerprint += take_individual_rdf(i, t2)
fingerprint /= len(typedic[t1])
if self.dimensions > 0:
fingerprint -= 1
fingerprints[key] = fingerprint
return [fingerprints, typedic]
class LennardJones(Calculator):
"""Lennard Jones potential calculator
see https://en.wikipedia.org/wiki/Lennard-Jones_potential
The fundamental definition of this potential is a pairwise energy:
``u_ij = 4 epsilon ( sigma^12/r_ij^12 - sigma^6/r_ij^6 )``
For convenience, we'll use d_ij to refer to "distance vector" and
``r_ij`` to refer to "scalar distance". So, with position vectors `r_i`:
``r_ij = | r_j - r_i | = | d_ij |``
The derivative of u_ij is:
::
d u_ij / d r_ij
= (-24 epsilon / r_ij) ( sigma^12/r_ij^12 - sigma^6/r_ij^6 )
We can define a pairwise force
``f_ij = d u_ij / d d_ij = d u_ij / d r_ij * d_ij / r_ij``
The terms in front of d_ij are often combined into a "general derivative"
``du_ij = (d u_ij / d d_ij) / r_ij``
The force on an atom is:
``f_i = sum_(j != i) f_ij``
There is some freedom of choice in assigning atomic energies, i.e.
choosing a way to partition the total energy into atomic contributions.
We choose a symmetric approach:
``u_i = 1/2 sum_(j != i) u_ij``
The total energy of a system of atoms is then:
``u = sum_i u_i = 1/2 sum_(i, j != i) u_ij``
The stress can be written as ( `(x)` denoting outer product):
``sigma = 1/2 sum_(i, j != i) f_ij (x) d_ij = sum_i sigma_i ,``
with atomic contributions
``sigma_i = 1/2 sum_(j != i) f_ij (x) d_ij``
Implementation note:
For computational efficiency, we minimise the number of
pairwise evaluations, so we iterate once over all the atoms,
and use NeighbourList with bothways=False. In terms of the
equations, we therefore effectively restrict the sum over `i != j`
to `j > i`, and need to manually re-add the "missing" `j < i` contributions.
Another consideration is the cutoff. We have to ensure that the potential
goes to zero smoothly as an atom moves across the cutoff threshold,
otherwise the potential is not continuous. In cases where the cutoff is
so large that u_ij is very small at the cutoff this is automatically
ensured, but in general, `u_ij(rc) != 0`.
In order to catch this case, this implementation shifts the total energy
``u'_ij = u_ij - u_ij(rc)``
which ensures that it is precisely zero at the cutoff.
However, this means that the energy effectively depends
on the cutoff, which might lead to unexpected results!
"""
implemented_properties = [
'energy', 'atomic_energies', 'forces', 'free_energy'
]
implemented_properties += ['stress', 'stresses'] # bulk properties
default_parameters = {'epsilon': 1.0, 'sigma': 1.0, 'rc': None}
nolabel = True
def __init__(self, **kwargs):
"""
Parameters
----------
sigma: float
The potential minimum is at 2**(1/6) * sigma, default 1.0
epsilon: float
The potential depth, default 1.0
rc: float, None
Cut-off for the NeighborList is set to 3 * sigma if None.
The energy is upshifted to be continuous at rc.
Default None
"""
Calculator.__init__(self, **kwargs)
if self.parameters.rc is None:
self.parameters.rc = 3 * self.parameters.sigma
self.nl = None
def calculate(
self,
atoms=None,
properties=None,
system_changes=all_changes,
):
if properties is None:
properties = self.implemented_properties
Calculator.calculate(self, atoms, properties, system_changes)
natoms = len(self.atoms)
sigma = self.parameters.sigma
epsilon = self.parameters.epsilon
rc = self.parameters.rc
if self.nl is None or 'numbers' in system_changes:
self.nl = NeighborList([rc / 2] * natoms, self_interaction=False)
self.nl.update(self.atoms)
positions = self.atoms.positions
cell = self.atoms.cell
# potential value at rc
e0 = 4 * epsilon * ((sigma / rc)**12 - (sigma / rc)**6)
atomic_energies = np.zeros(natoms)
forces = np.zeros((natoms, 3))
stresses = np.zeros((natoms, 3, 3))
for ii in range(natoms):
neighbors, offsets = self.nl.get_neighbors(ii)
cells = np.dot(offsets, cell)
# pointing *towards* neighbours
distance_vectors = positions[neighbors] + cells - positions[ii]
r2 = (distance_vectors**2).sum(1)
c6 = (sigma**2 / r2)**3
c6[r2 > rc**2] = 0.0
c12 = c6**2
pairwise_energies = 4 * epsilon * (c12 - c6) - e0 * (c6 != 0.0)
atomic_energies[ii] += 0.5 * pairwise_energies.sum(
) # atomic energies
pairwise_forces = (-24 * epsilon * (2 * c12 - c6) /
r2)[:, np.newaxis] * distance_vectors
forces[ii] += pairwise_forces.sum(axis=0)
stresses[ii] += 0.5 * np.dot(
pairwise_forces.T,
distance_vectors) # equivalent to outer product
# add j < i contributions
for jj, atom_j in enumerate(neighbors):
atomic_energies[atom_j] += 0.5 * pairwise_energies[jj]
forces[atom_j] += -pairwise_forces[jj] # f_ji = - f_ij
stresses[atom_j] += 0.5 * np.outer(pairwise_forces[jj],
distance_vectors[jj])
# no lattice, no stress
if self.atoms.number_of_lattice_vectors == 3:
stresses = full_3x3_to_voigt_6_stress(stresses)
self.results['stress'] = (stresses.sum(axis=0) /
self.atoms.get_volume())
self.results['stresses'] = stresses / self.atoms.get_volume()
energy = atomic_energies.sum()
self.results['energy'] = energy
self.results['atomic_energies'] = atomic_energies
self.results['free_energy'] = energy
self.results['forces'] = forces
def initialize(self, atoms):
self.par = {}
self.rc = 0.0
self.numbers = atoms.get_atomic_numbers()
if self.parameters.asap_cutoff:
relevant_pars = {}
for symb, p in parameters.items():
if atomic_numbers[symb] in self.numbers:
relevant_pars[symb] = p
else:
relevant_pars = parameters
maxseq = max(par[1] for par in relevant_pars.values()) * Bohr
rc = self.rc = beta * maxseq * 0.5 * (sqrt(3) + sqrt(4))
rr = rc * 2 * sqrt(4) / (sqrt(3) + sqrt(4))
self.acut = np.log(9999.0) / (rr - rc)
if self.parameters.asap_cutoff:
self.rc_list = self.rc * 1.045
else:
self.rc_list = self.rc + 0.5
for Z in self.numbers:
if Z not in self.par:
sym = chemical_symbols[Z]
if sym not in parameters:
raise NotImplementedError(
'No EMT-potential for {0}'.format(sym))
p = parameters[sym]
s0 = p[1] * Bohr
eta2 = p[3] / Bohr
kappa = p[4] / Bohr
x = eta2 * beta * s0
gamma1 = 0.0
gamma2 = 0.0
for i, n in enumerate([12, 6, 24]):
r = s0 * beta * sqrt(i + 1)
x = n / (12 * (1.0 + exp(self.acut * (r - rc))))
gamma1 += x * exp(-eta2 * (r - beta * s0))
gamma2 += x * exp(-kappa / beta * (r - beta * s0))
self.par[Z] = {
'E0': p[0],
's0': s0,
'V0': p[2],
'eta2': eta2,
'kappa': kappa,
'lambda': p[5] / Bohr,
'n0': p[6] / Bohr**3,
'rc': rc,
'gamma1': gamma1,
'gamma2': gamma2
}
self.ksi = {}
for s1, p1 in self.par.items():
self.ksi[s1] = {}
for s2, p2 in self.par.items():
self.ksi[s1][s2] = p2['n0'] / p1['n0']
self.forces = np.empty((len(atoms), 3))
self.stress = np.empty((3, 3))
self.sigma1 = np.empty(len(atoms))
self.deds = np.empty(len(atoms))
self.nl = NeighborList([0.5 * self.rc_list] * len(atoms),
self_interaction=False)
def insertHbyList(ase_struct,
pmd_top,
implicitHbondingPartners,
bond_length=1.0,
debug=False):
# make copies of passed structures as not to alter originals:
new_pmd_top = pmd_top.copy(pmd.Structure)
new_ase_struct = ase_struct.copy()
# names stores the String IDs of all atoms as to facilitate later ASE ID -> Atom name mapping
names = [a.name for a in pmd_top.atoms]
residues = [a.residue.name for a in pmd_top.atoms]
# make copied atoms accessible by unchangable indices (standard list)
originalAtoms = [a for a in new_pmd_top.atoms]
implicitHbondingPartnersIdxHnoTuples = [
(a.idx, implicitHbondingPartners[k]) for a in pmd_top.atoms
for k in implicitHbondingPartners.keys() if a.name == k
]
implicitHbondingPartnersIdxHnoDict = dict(
implicitHbondingPartnersIdxHnoTuples)
# build numbered neighbour list "manually"
#i: list of atoms e.g. [0,0,0,1,1,2,2,...]
i = np.array([b.atom1.idx for b in new_pmd_top.bonds])
#j: list of bonding partners corresponding to i [1,2,3,...] ==> 0 has bondpartners 1,2 and 3; etc.
j = np.array([b.atom2.idx for b in new_pmd_top.bonds])
r = new_ase_struct.positions
for k, Hno in implicitHbondingPartnersIdxHnoDict.items(
): # for all atoms to append hydrogen to
logging.info('Adding {} H-atoms to {} (#{})...'.format(
Hno, originalAtoms[k].name, k))
for h in range(0, Hno):
r = new_ase_struct.positions
bondingPartners = j[i == k]
logging.info('bondingPartners {}'.format(bondingPartners))
partnerStr = ''
for p in bondingPartners:
if partnerStr == '':
partnerStr = originalAtoms[p].name
else:
partnerStr += ', ' + originalAtoms[p].name
logging.info('Atom {} already has bonding partners {}'.format(
originalAtoms[k].name, partnerStr))
dr = (r[j[i == k]] - r[k]).mean(axis=0)
# my understanding: dr is vector
# from atom k's position towards the geometrical center of mass
# it forms with its defined neighbours
# r0 is a vector offset into the opposit direction:
dr = dr / np.linalg.norm(dr) #normalized vector in direction dr
#calculate an orthogonal vector 'dr_ortho' on dr
#and push the H atoms in dr+dr_ortho and dr-dr_ortho
#if one has to add more than two H atoms introduce dr_ortho_2 = dr x dr_ortho
dr_ortho = np.cross(dr, np.array([1, 0, 0]))
if np.linalg.norm(
dr_ortho
) < 0.1: #if dr and (1,0,0) have almost the same direction
dr_ortho = np.cross(dr, np.array([0, 1, 0]))
# (1-2*h) = {1,-1} for h={0,1}
h_pos_vec = (dr + (1 - 2 * h) * dr_ortho
) / np.linalg.norm(dr + (1 - 2 * h) * dr_ortho)
r0 = r[k] - bond_length * h_pos_vec
new_ase_struct += ase.Atom('H', r0) # add atom in ase structure
n_atoms = len(new_ase_struct)
#introduce a corrector step for a added atom which is too close to others
#do as many corrector stepps until all atoms are more than 1\AA appart
c_step = 0
while True:
nl = NeighborList(cutoffs=[.5] * len(new_ase_struct),
skin=0.09,
self_interaction=False,
bothways=True)
nl.update(new_ase_struct)
indices, offsets = nl.get_neighbors(-1)
indices = np.delete(indices, np.where(indices == k))
if len(indices) == 0:
break
elif c_step > 15:
logging.info(
'programm needs more than 15 corrector steps for H atom {} at atom {}'
.format(n_atoms, k))
sys.exit(15)
break
logging.info('too close atoms {}'.format(indices))
c_step += 1
logging.info('correcter step {} for H {} at atom {}'.format(
c_step, n_atoms - 1, k))
# if indices not empty -> the atom(-1)=r_H is to close together
# with atom a_close=indices[0], it is a H-atom belonging to atom 'k'=r_k .
#correctorstep: corr_step = (r_H-a_close)/|(r_H-a_close)|
#corrected_pos: corr_pos = ((r_H-r_k) + corr_step)/|((r_H-r_k) + corr_step)|
#new H position: new_r_H = r_k + corr_pos
r_H, r_k, a_close = np.take(new_ase_struct.get_positions(),
[-1, k, indices[0]],
axis=0)
#print('r_H, r_k, a_close', r_H, r_k, a_close)
corr_step = (r_H - a_close) / np.linalg.norm(
(r_H - a_close)
) #maybe introduce here a skaling Faktor s=0.3 or somthing like that to make tiny corrections and don't overshoot.
corr_pos = ((r_H - r_k) + corr_step) / np.linalg.norm(
(r_H - r_k) + corr_step)
new_r_H = r_k + bond_length * corr_pos
#correct the H position to new_r_H in new_ase_struct
trans = np.zeros([n_atoms, 3])
trans[-1] = new_r_H - r_H
new_ase_struct.translate(trans)
#view(new_ase_struct)
#sys.exit()
i = np.append(i, k) # manually update numbered neighbour lists
j = np.append(j, len(new_ase_struct) - 1)
# update pmd topology
bondingPartner = originalAtoms[
k] # here we need the original numbering,
# as ParmEd alters indices when adding atoms to the structure
nameH = '{}{}'.format(
h + 1, bondingPartner.name) # atom needs a unique name
logging.info('Adding H-atom {} at position [ {}, {}, {} ]'.format(
nameH, r0[0], r0[1], r0[2]))
new_H = pmd.Atom(name=nameH, type='H', atomic_number=1)
new_H.xx = r0[
0] # ParmEd documentation not very helpful, did not find any more compact assignment
new_H.xy = r0[1]
new_H.xz = r0[2]
# do not understand ParmEd that well, apparently we need the Bond object in order to update topology
new_Bond = pmd.Bond(bondingPartner, new_H)
new_H.bond_to(
bondingPartner) # not sure, whether this is necessary
new_pmd_top.bonds.append(new_Bond)
new_pmd_top.add_atom_to_residue(new_H, bondingPartner.residue)
originalAtoms.append(
new_H) # add atom to the bottom of "index-stiff" list
names.append(nameH) # append name of H-atom
residues.append(bondingPartner.residue.name
) # H is in same residue as bonding partner
return new_ase_struct, new_pmd_top, names, residues
class OPLSff:
def __init__(self, fileobj=None, warnings=0):
self.warnings = warnings
self.data = {}
if fileobj is not None:
self.read(fileobj)
def read(self, fileobj, comments='#'):
if isinstance(fileobj, str):
fileobj = open(fileobj)
def read_block(name, symlen, nvalues):
"""Read a data block.
name: name of the block to store in self.data
symlen: length of the symbol
nvalues: number of values expected
"""
if name not in self.data:
self.data[name] = {}
data = self.data[name]
def add_line():
line = fileobj.readline().strip()
if not len(line): # end of the block
return False
line = line.split('#')[0] # get rid of comments
if len(line) > symlen:
symbol = line[:symlen]
words = line[symlen:].split()
if len(words) >= nvalues:
if nvalues == 1:
data[symbol] = float(words[0])
else:
data[symbol] = [float(word)
for word in words[:nvalues]]
return True
while add_line():
pass
read_block('one', 2, 3)
read_block('bonds', 5, 2)
read_block('angles', 8, 2)
read_block('dihedrals', 11, 4)
read_block('cutoffs', 5, 1)
self.bonds = BondData(self.data['bonds'])
self.angles = AnglesData(self.data['angles'])
self.dihedrals = DihedralsData(self.data['dihedrals'])
self.cutoffs = CutoffList(self.data['cutoffs'])
def write_lammps(self, atoms, prefix='lammps'):
"""Write input for a LAMMPS calculation."""
self.prefix = prefix
if hasattr(atoms, 'connectivities'):
connectivities = atoms.connectivities
else:
btypes, blist = self.get_bonds(atoms)
atypes, alist = self.get_angles()
dtypes, dlist = self.get_dihedrals(alist, atypes)
connectivities = {
'bonds': blist,
'bond types': btypes,
'angles': alist,
'angle types': atypes,
'dihedrals': dlist,
'dihedral types': dtypes,
}
self.write_lammps_definitions(atoms, btypes, atypes, dtypes)
self.write_lammps_in()
self.write_lammps_atoms(atoms, connectivities)
def write_lammps_in(self):
fileobj = self.prefix + '_in'
if isinstance(fileobj, str):
fileobj = open(fileobj, 'w')
fileobj.write("""# LAMMPS relaxation (written by ASE)
units metal
atom_style full
boundary p p p
#boundary p p f
""")
fileobj.write('read_data ' + self.prefix + '_atoms\n')
fileobj.write('include ' + self.prefix + '_opls\n')
fileobj.write("""
kspace_style pppm 1e-5
#kspace_modify slab 3.0
neighbor 1.0 bin
neigh_modify delay 0 every 1 check yes
thermo 1000
thermo_style custom step temp press cpu pxx pyy pzz pxy pxz pyz ke pe etotal vol lx ly lz atoms
dump 1 all xyz 1000 dump_relax.xyz
dump_modify 1 sort id
restart 100000 test_relax
min_style fire
minimize 1.0e-14 1.0e-5 100000 100000
""")
fileobj.close()
def write_lammps_atoms(self, atoms, connectivities):
"""Write atoms input for LAMMPS"""
fname = self.prefix + '_atoms'
fileobj = open(fname, 'w')
# header
fileobj.write(fileobj.name + ' (by ' + str(self.__class__) + ')\n\n')
fileobj.write(str(len(atoms)) + ' atoms\n')
fileobj.write(str(len(atoms.types)) + ' atom types\n')
blist = connectivities['bonds']
if len(blist):
btypes = connectivities['bond types']
fileobj.write(str(len(blist)) + ' bonds\n')
fileobj.write(str(len(btypes)) + ' bond types\n')
alist = connectivities['angles']
if len(alist):
atypes = connectivities['angle types']
fileobj.write(str(len(alist)) + ' angles\n')
fileobj.write(str(len(atypes)) + ' angle types\n')
dlist = connectivities['dihedrals']
if len(dlist):
dtypes = connectivities['dihedral types']
fileobj.write(str(len(dlist)) + ' dihedrals\n')
fileobj.write(str(len(dtypes)) + ' dihedral types\n')
# cell
p = Prism(atoms.get_cell())
xhi, yhi, zhi, xy, xz, yz = p.get_lammps_prism_str()
fileobj.write('\n0.0 %s xlo xhi\n' % xhi)
fileobj.write('0.0 %s ylo yhi\n' % yhi)
fileobj.write('0.0 %s zlo zhi\n' % zhi)
# atoms
fileobj.write('\nAtoms\n\n')
tag = atoms.get_tags()
if atoms.has('molid'):
molid = atoms.get_array('molid')
else:
molid = [1] * len(atoms)
for i, r in enumerate(map(p.pos_to_lammps_str,
atoms.get_positions())):
q = self.data['one'][atoms.types[tag[i]]][2]
fileobj.write('%6d %3d %3d %s %s %s %s' % ((i + 1, molid[i],
tag[i] + 1,
q)
+ tuple(r)))
fileobj.write(' # ' + atoms.types[tag[i]] + '\n')
# velocities
velocities = atoms.get_velocities()
if velocities is not None:
fileobj.write('\nVelocities\n\n')
for i, v in enumerate(velocities):
fileobj.write('%6d %g %g %g\n' %
(i + 1, v[0], v[1], v[2]))
# masses
fileobj.write('\nMasses\n\n')
for i, typ in enumerate(atoms.types):
cs = atoms.split_symbol(typ)[0]
fileobj.write('%6d %g # %s -> %s\n' %
(i + 1,
atomic_masses[chemical_symbols.index(cs)],
typ, cs))
# bonds
if len(blist):
fileobj.write('\nBonds\n\n')
for ib, bvals in enumerate(blist):
fileobj.write('%8d %6d %6d %6d ' %
(ib + 1, bvals[0] + 1, bvals[1] + 1,
bvals[2] + 1))
try:
fileobj.write('# ' + btypes[bvals[0]])
except:
pass
fileobj.write('\n')
# angles
if len(alist):
fileobj.write('\nAngles\n\n')
for ia, avals in enumerate(alist):
fileobj.write('%8d %6d %6d %6d %6d ' %
(ia + 1, avals[0] + 1,
avals[1] + 1, avals[2] + 1, avals[3] + 1))
try:
fileobj.write('# ' + atypes[avals[0]])
except:
pass
fileobj.write('\n')
# dihedrals
if len(dlist):
fileobj.write('\nDihedrals\n\n')
for i, dvals in enumerate(dlist):
fileobj.write('%8d %6d %6d %6d %6d %6d ' %
(i + 1, dvals[0] + 1,
dvals[1] + 1, dvals[2] + 1,
dvals[3] + 1, dvals[4] + 1))
try:
fileobj.write('# ' + dtypes[dvals[0]])
except:
pass
fileobj.write('\n')
def update_neighbor_list(self, atoms):
cut = 0.5 * max(self.data['cutoffs'].values())
self.nl = NeighborList([cut] * len(atoms), skin=0,
bothways=True, self_interaction=False)
self.nl.update(atoms)
self.atoms = atoms
def get_bonds(self, atoms):
"""Find bonds and return them and their types"""
cutoffs = CutoffList(self.data['cutoffs'])
self.update_neighbor_list(atoms)
types = atoms.get_types()
tags = atoms.get_tags()
cell = atoms.get_cell()
bond_list = []
bond_types = []
for i, atom in enumerate(atoms):
iname = types[tags[i]]
indices, offsets = self.nl.get_neighbors(i)
for j, offset in zip(indices, offsets):
if j <= i:
continue # do not double count
jname = types[tags[j]]
cut = cutoffs.value(iname, jname)
if cut is None:
if self.warnings > 1:
print('Warning: cutoff %s-%s not found'
% (iname, jname))
continue # don't have it
dist = np.linalg.norm(atom.position - atoms[j].position
- np.dot(offset, cell))
if dist > cut:
continue # too far away
name, val = self.bonds.name_value(iname, jname)
if name is None:
if self.warnings:
print('Warning: potential %s-%s not found'
% (iname, jname))
continue # don't have it
if name not in bond_types:
bond_types.append(name)
bond_list.append([bond_types.index(name), i, j])
return bond_types, bond_list
def get_angles(self, atoms=None):
cutoffs = CutoffList(self.data['cutoffs'])
if atoms is not None:
self.update_neighbor_list(atoms)
else:
atoms = self.atoms
types = atoms.get_types()
tags = atoms.get_tags()
cell = atoms.get_cell()
ang_list = []
ang_types = []
# center atom *-i-*
for i, atom in enumerate(atoms):
iname = types[tags[i]]
indicesi, offsetsi = self.nl.get_neighbors(i)
# search for first neighbor j-i-*
for j, offsetj in zip(indicesi, offsetsi):
jname = types[tags[j]]
cut = cutoffs.value(iname, jname)
if cut is None:
continue # don't have it
dist = np.linalg.norm(atom.position - atoms[j].position
- np.dot(offsetj, cell))
if dist > cut:
continue # too far away
# search for second neighbor j-i-k
for k, offsetk in zip(indicesi, offsetsi):
if k <= j:
continue # avoid double count
kname = types[tags[k]]
cut = cutoffs.value(iname, kname)
if cut is None:
continue # don't have it
dist = np.linalg.norm(atom.position -
np.dot(offsetk, cell) -
atoms[k].position)
if dist > cut:
continue # too far away
name, val = self.angles.name_value(jname, iname,
kname)
if name is None:
if self.warnings > 1:
print('Warning: angles %s-%s-%s not found'
% (jname, iname, kname))
continue # don't have it
if name not in ang_types:
ang_types.append(name)
ang_list.append([ang_types.index(name), j, i, k])
return ang_types, ang_list
def get_dihedrals(self, ang_types, ang_list):
'Dihedrals derived from angles.'
cutoffs = CutoffList(self.data['cutoffs'])
atoms = self.atoms
types = atoms.get_types()
tags = atoms.get_tags()
cell = atoms.get_cell()
dih_list = []
dih_types = []
def append(name, i, j, k, l):
if name not in dih_types:
dih_types.append(name)
index = dih_types.index(name)
if (([index, i, j, k, l] not in dih_list) and
([index, l, k, j, i] not in dih_list)):
dih_list.append([index, i, j, k, l])
for angle in ang_types:
l, i, j, k = angle
iname = types[tags[i]]
jname = types[tags[j]]
kname = types[tags[k]]
# search for l-i-j-k
indicesi, offsetsi = self.nl.get_neighbors(i)
for l, offsetl in zip(indicesi, offsetsi):
if l == j:
continue # avoid double count
lname = types[tags[l]]
cut = cutoffs.value(iname, lname)
if cut is None:
continue # don't have it
dist = np.linalg.norm(atoms[i].position - atoms[l].position
- np.dot(offsetl, cell))
if dist > cut:
continue # too far away
name, val = self.dihedrals.name_value(lname, iname,
jname, kname)
if name is None:
continue # don't have it
append(name, l, i, j, k)
# search for i-j-k-l
indicesk, offsetsk = self.nl.get_neighbors(k)
for l, offsetl in zip(indicesk, offsetsk):
if l == j:
continue # avoid double count
lname = types[tags[l]]
cut = cutoffs.value(kname, lname)
if cut is None:
continue # don't have it
dist = np.linalg.norm(atoms[k].position - atoms[l].position
- np.dot(offsetl, cell))
if dist > cut:
continue # too far away
name, val = self.dihedrals.name_value(iname, jname,
kname, lname)
if name is None:
continue # don't have it
append(name, i, j, k, l)
return dih_types, dih_list
def write_lammps_definitions(self, atoms, btypes, atypes, dtypes):
"""Write force field definitions for LAMMPS."""
fileobj = self.prefix + '_opls'
if isinstance(fileobj, str):
fileobj = open(fileobj, 'w')
fileobj.write('# OPLS potential\n')
fileobj.write('# write_lammps' +
str(time.asctime(
time.localtime(time.time()))))
# bonds
if len(btypes):
fileobj.write('\n# bonds\n')
fileobj.write('bond_style harmonic\n')
for ib, btype in enumerate(btypes):
fileobj.write('bond_coeff %6d' % (ib + 1))
for value in self.bonds.nvh[btype]:
fileobj.write(' ' + str(value))
fileobj.write(' # ' + btype + '\n')
# angles
if len(atypes):
fileobj.write('\n# angles\n')
fileobj.write('angle_style harmonic\n')
for ia, atype in enumerate(atypes):
fileobj.write('angle_coeff %6d' % (ia + 1))
for value in self.angles.nvh[atype]:
fileobj.write(' ' + str(value))
fileobj.write(' # ' + atype + '\n')
# dihedrals
if len(dtypes):
fileobj.write('\n# dihedrals\n')
fileobj.write('dihedral_style opls\n')
for i, dtype in enumerate(dtypes):
fileobj.write('dihedral_coeff %6d' % (i + 1))
for value in self.dihedrals.nvh[dtype]:
fileobj.write(' ' + str(value))
fileobj.write(' # ' + dtype + '\n')
# Lennard Jones settings
fileobj.write('\n# L-J parameters\n')
fileobj.write('pair_style lj/cut/coul/long 10.0 7.4' +
' # consider changing these parameters\n')
fileobj.write('special_bonds lj/coul 0.0 0.0 0.5\n')
data = self.data['one']
for ia, atype in enumerate(atoms.types):
if len(atype) < 2:
atype = atype + ' '
fileobj.write('pair_coeff ' + str(ia + 1) + ' ' + str(ia + 1))
for value in data[atype][:2]:
fileobj.write(' ' + str(value))
fileobj.write(' # ' + atype + '\n')
fileobj.write('pair_modify shift yes mix geometric\n')
# Charges
fileobj.write('\n# charges\n')
for ia, atype in enumerate(atoms.types):
if len(atype) < 2:
atype = atype + ' '
fileobj.write('set type ' + str(ia + 1))
fileobj.write(' charge ' + str(data[atype][2]))
fileobj.write(' # ' + atype + '\n')
class EMT(Calculator):
"""Python implementation of the Effective Medium Potential.
Supports the following standard EMT metals:
Al, Cu, Ag, Au, Ni, Pd and Pt.
In addition, the following elements are supported.
They are NOT well described by EMT, and the parameters
are not for any serious use:
H, C, N, O
The potential takes a single argument, ``asap_cutoff``
(default: False). If set to True, the cutoff mimics
how Asap does it; most importantly the global cutoff
is chosen from the largest atom present in the simulation,
if False it is chosen from the largest atom in the parameter
table. True gives the behaviour of the Asap code and
older EMT implementations, although the results are not
bitwise identical.
"""
implemented_properties = ['energy', 'forces']
nolabel = True
default_parameters = {'asap_cutoff': False}
def __init__(self, **kwargs):
Calculator.__init__(self, **kwargs)
def initialize(self, atoms):
self.par = {}
self.rc = 0.0
self.numbers = atoms.get_atomic_numbers()
if self.parameters.asap_cutoff:
relevant_pars = {}
for symb, p in parameters.items():
if atomic_numbers[symb] in self.numbers:
relevant_pars[symb] = p
else:
relevant_pars = parameters
maxseq = max(par[1] for par in relevant_pars.values()) * Bohr
rc = self.rc = beta * maxseq * 0.5 * (sqrt(3) + sqrt(4))
rr = rc * 2 * sqrt(4) / (sqrt(3) + sqrt(4))
self.acut = np.log(9999.0) / (rr - rc)
if self.parameters.asap_cutoff:
self.rc_list = self.rc * 1.045
else:
self.rc_list = self.rc + 0.5
for Z in self.numbers:
if Z not in self.par:
sym = chemical_symbols[Z]
if sym not in parameters:
raise NotImplementedError('No EMT-potential for {0}'
.format(sym))
p = parameters[sym]
s0 = p[1] * Bohr
eta2 = p[3] / Bohr
kappa = p[4] / Bohr
x = eta2 * beta * s0
gamma1 = 0.0
gamma2 = 0.0
for i, n in enumerate([12, 6, 24]):
r = s0 * beta * sqrt(i + 1)
x = n / (12 * (1.0 + exp(self.acut * (r - rc))))
gamma1 += x * exp(-eta2 * (r - beta * s0))
gamma2 += x * exp(-kappa / beta * (r - beta * s0))
self.par[Z] = {'E0': p[0],
's0': s0,
'V0': p[2],
'eta2': eta2,
'kappa': kappa,
'lambda': p[5] / Bohr,
'n0': p[6] / Bohr**3,
'rc': rc,
'gamma1': gamma1,
'gamma2': gamma2}
self.ksi = {}
for s1, p1 in self.par.items():
self.ksi[s1] = {}
for s2, p2 in self.par.items():
self.ksi[s1][s2] = p2['n0'] / p1['n0']
self.forces = np.empty((len(atoms), 3))
self.sigma1 = np.empty(len(atoms))
self.deds = np.empty(len(atoms))
self.nl = NeighborList([0.5 * self.rc_list] * len(atoms),
self_interaction=False)
def calculate(self, atoms=None, properties=['energy'],
system_changes=all_changes):
Calculator.calculate(self, atoms, properties, system_changes)
if 'numbers' in system_changes:
self.initialize(self.atoms)
positions = self.atoms.positions
numbers = self.atoms.numbers
cell = self.atoms.cell
self.nl.update(self.atoms)
self.energy = 0.0
self.sigma1[:] = 0.0
self.forces[:] = 0.0
natoms = len(self.atoms)
for a1 in range(natoms):
Z1 = numbers[a1]
p1 = self.par[Z1]
ksi = self.ksi[Z1]
neighbors, offsets = self.nl.get_neighbors(a1)
offsets = np.dot(offsets, cell)
for a2, offset in zip(neighbors, offsets):
d = positions[a2] + offset - positions[a1]
r = sqrt(np.dot(d, d))
if r < self.rc_list:
Z2 = numbers[a2]
p2 = self.par[Z2]
self.interact1(a1, a2, d, r, p1, p2, ksi[Z2])
for a in range(natoms):
Z = numbers[a]
p = self.par[Z]
try:
ds = -log(self.sigma1[a] / 12) / (beta * p['eta2'])
except (OverflowError, ValueError):
self.deds[a] = 0.0
self.energy -= p['E0']
continue
x = p['lambda'] * ds
y = exp(-x)
z = 6 * p['V0'] * exp(-p['kappa'] * ds)
self.deds[a] = ((x * y * p['E0'] * p['lambda'] + p['kappa'] * z) /
(self.sigma1[a] * beta * p['eta2']))
self.energy += p['E0'] * ((1 + x) * y - 1) + z
for a1 in range(natoms):
Z1 = numbers[a1]
p1 = self.par[Z1]
ksi = self.ksi[Z1]
neighbors, offsets = self.nl.get_neighbors(a1)
offsets = np.dot(offsets, cell)
for a2, offset in zip(neighbors, offsets):
d = positions[a2] + offset - positions[a1]
r = sqrt(np.dot(d, d))
if r < self.rc_list:
Z2 = numbers[a2]
p2 = self.par[Z2]
self.interact2(a1, a2, d, r, p1, p2, ksi[Z2])
self.results['energy'] = self.energy
self.results['free_energy'] = self.energy
self.results['forces'] = self.forces
def interact1(self, a1, a2, d, r, p1, p2, ksi):
x = exp(self.acut * (r - self.rc))
theta = 1.0 / (1.0 + x)
y1 = (0.5 * p1['V0'] * exp(-p2['kappa'] * (r / beta - p2['s0'])) *
ksi / p1['gamma2'] * theta)
y2 = (0.5 * p2['V0'] * exp(-p1['kappa'] * (r / beta - p1['s0'])) /
ksi / p2['gamma2'] * theta)
self.energy -= y1 + y2
f = ((y1 * p2['kappa'] + y2 * p1['kappa']) / beta +
(y1 + y2) * self.acut * theta * x) * d / r
self.forces[a1] += f
self.forces[a2] -= f
self.sigma1[a1] += (exp(-p2['eta2'] * (r - beta * p2['s0'])) *
ksi * theta / p1['gamma1'])
self.sigma1[a2] += (exp(-p1['eta2'] * (r - beta * p1['s0'])) /
ksi * theta / p2['gamma1'])
def interact2(self, a1, a2, d, r, p1, p2, ksi):
x = exp(self.acut * (r - self.rc))
theta = 1.0 / (1.0 + x)
y1 = (exp(-p2['eta2'] * (r - beta * p2['s0'])) *
ksi / p1['gamma1'] * theta * self.deds[a1])
y2 = (exp(-p1['eta2'] * (r - beta * p1['s0'])) /
ksi / p2['gamma1'] * theta * self.deds[a2])
f = ((y1 * p2['eta2'] + y2 * p1['eta2']) +
(y1 + y2) * self.acut * theta * x) * d / r
self.forces[a1] -= f
self.forces[a2] += f
class TestGeometry(unittest.TestCase):
"""Container for tests to the geometry module."""
def __init__(self, *args, **kwargs):
super(TestGeometry, self).__init__(*args, **kwargs)
def shortDescription(self):
"""Silences unittest from printing the docstrings in test cases."""
return None
def setUp(self):
"""Sets up some basic stuff which can be useful in the tests."""
cutoff = 3.0
self.structure = bulk('Al')
self.neighborlist = NeighborList(len(self.structure) * [cutoff / 2],
skin=1e-8,
bothways=True,
self_interaction=False)
self.neighborlist.update(self.structure)
def test_get_scaled_positions(self):
""" Tests the test_get_scaled_positions method. """
positions = np.array([[6.5, 5.1, 3.0], [-0.1, 1.3, 4.5], [0, 0, 0],
[15, 7, 4.5]])
cell = np.array([[4.0, 1.0, 0.1], [-0.4, 6.7, 0], [-4, 2, 16]])
retval = get_scaled_positions(positions, cell, wrap=False)
targetval = np.array([[1.84431247, 0.43339424, 0.17597305],
[0.26176336, 0.07149383, 0.27961398], [0, 0, 0],
[4.04248515, 0.36500685, 0.25598447]])
np.testing.assert_almost_equal(retval, targetval)
retval = get_scaled_positions(positions, cell, wrap=True)
targetval = np.array([[0.84431247, 0.43339424, 0.17597305],
[0.26176336, 0.07149383, 0.27961398], [0, 0, 0],
[0.04248515, 0.36500685, 0.25598447]])
np.testing.assert_almost_equal(retval, targetval)
retval = get_scaled_positions(positions,
cell,
wrap=True,
pbc=3 * [False])
targetval = np.array([[1.84431247, 0.43339424, 0.17597305],
[0.26176336, 0.07149383, 0.27961398], [0, 0, 0],
[4.04248515, 0.36500685, 0.25598447]])
np.testing.assert_almost_equal(retval, targetval)
retval = get_scaled_positions(positions,
cell,
wrap=True,
pbc=[True, True, False])
targetval = np.array([[0.84431247, 0.43339424, 0.17597305],
[0.26176336, 0.07149383, 0.27961398], [0, 0, 0],
[0.04248515, 0.36500685, 0.25598447]])
np.testing.assert_almost_equal(retval, targetval)
def test_get_primitive_structure(self) -> None:
""" Tests the get_primitive_structure method. """
def compare_structures(s1: Atoms, s2: Atoms) -> bool:
if len(s1) != len(s2):
return False
if not np.all(np.isclose(s1.cell, s2.cell)):
return False
if not np.all(
np.isclose(s1.get_scaled_positions(),
s2.get_scaled_positions())):
return False
if not np.all(
s1.get_chemical_symbols() == s2.get_chemical_symbols()):
return False
return True
structure = bulk('Al', crystalstructure='fcc', a=4).repeat(2)
retval = get_primitive_structure(structure,
no_idealize=True,
to_primitive=True)
targetval = Atoms('Al',
cell=[[0.0, 2.0, 2.0], [2.0, 0.0, 2.0],
[2.0, 2.0, 0.0]],
pbc=True,
positions=[[0, 0, 0]])
self.assertTrue(compare_structures(retval, targetval))
structure = bulk('Al', crystalstructure='fcc', a=4).repeat(2)
noise_level = 1e-3
structure[0].position += noise_level * np.array([1, -5, 3])
structure[3].position += noise_level * np.array([-2, 3, -1])
retval = get_primitive_structure(structure,
no_idealize=True,
to_primitive=True)
targetval = Atoms(8 * 'Al',
cell=[[-4.0, 0.0, -4.0], [-4.0, 4.0, 0.0],
[0.0, 4.0, -4.0]],
pbc=True,
positions=[[-3.999e+00, 7.995e+00, -3.997e+00],
[-2.000e+00, 2.000e+00, -4.000e+00],
[-2.000e+00, 0.000e+00, -2.000e+00],
[-2.000e-03, 2.003e+00, -2.001e+00],
[-4.000e+00, 2.000e+00, -2.000e+00],
[-2.000e+00, 4.000e+00, -2.000e+00],
[-2.000e+00, 2.000e+00, 0.000e+00],
[-4.000e+00, 4.000e+00, -4.000e+00]])
self.assertTrue(compare_structures(retval, targetval))
structure = bulk('Al', crystalstructure='fcc', a=4).repeat(2)
noise_level = 1e-7
structure[0].position += noise_level * np.array([1, -5, 3])
structure[3].position += noise_level * np.array([-2, 3, -1])
retval = get_primitive_structure(structure,
no_idealize=True,
to_primitive=True)
targetval = Atoms(
'Al',
cell=[[0.0, 2.0, 2.0], [2.0, 0.0, 2.0], [2.0, 2.0, 0.0]],
pbc=True,
positions=[[-1.24999998e-08, -2.49999997e-08, 2.50000001e-08]])
self.assertTrue(compare_structures(retval, targetval))
structure = bulk('SiC', crystalstructure='zincblende', a=4).repeat(
(2, 2, 1))
structure.pbc = [True, True, False]
retval = get_primitive_structure(structure,
no_idealize=True,
to_primitive=True)
targetval = Atoms('SiC',
cell=[[0.0, 2.0, 2.0], [2.0, 0.0, 2.0],
[2.0, 2.0, 0.0]],
pbc=[True, True, False],
positions=[[0, 0, 0], [1, 1, 1]])
self.assertTrue(compare_structures(retval, targetval))
structure = bulk('SiC', crystalstructure='zincblende', a=4).repeat(
(2, 2, 1))
structure.pbc = [True, True, False]
retval = get_primitive_structure(structure,
no_idealize=True,
to_primitive=False)
targetval = Atoms(4 * 'SiC',
cell=[4, 4, 4],
pbc=[True, True, False],
positions=[[0, 0, 0], [1, 1, 1], [0, 2,
2], [1, 3, 3],
[2, 0, 2], [3, 1, 3], [2, 2, 0],
[3, 3, 1]])
self.assertTrue(compare_structures(retval, targetval))
structure = bulk('SiC', crystalstructure='zincblende', a=4)
structure.cell = [[0.0, 2.0, 2.0], [2.0, 0.0, 2.0],
[2.0, 2.0, 0.00001]]
retval = get_primitive_structure(structure,
no_idealize=False,
to_primitive=True,
symprec=1e-3)
targetval = Atoms('SiC',
cell=[[0.0, 1.9999983333374998, 1.9999983333374998],
[1.9999983333374998, 0.0, 1.9999983333374998],
[1.9999983333374998, 1.9999983333374998, 0.0]],
pbc=[True, True, False],
positions=[[0, 0, 0],
[0.99999917, 0.99999917, 0.99999917]])
self.assertTrue(compare_structures(retval, targetval))
# Catch failure from spglib due to large symprec
symprec = 0.3
prim = bulk('Au', a=1.0, cubic=True)
prim[0].position += [0, 0, 0.01]
prim[1].position += [-0.01, 0, 0.01]
prim[2].position += [0, 0.01, 0.01]
prim[3].position += [0, 0, -0.01]
prim.cell[0][0] += 0.002
with self.assertRaises(ValueError) as cm:
get_primitive_structure(prim, symprec=symprec)
self.assertIn('spglib failed to find the primitive cell',
str(cm.exception))
def test_fractional_to_cartesian(self):
"""Tests the geometry function fractional_to_cartesian."""
# reference data
structure = bulk('Al')
frac_pos = np.array([[0.0, 0.0, -0.0], [0.0, 0.0, 1.0],
[0.0, 1.0, -1.0], [0.0, 1.0, -0.0],
[1.0, -1.0, -0.0], [1.0, 0.0, -1.0],
[1.0, 0.0, -0.0], [0.0, 0.0, -1.0],
[0.0, -1.0, 1.0], [0.0, -1.0, -0.0],
[-1.0, 1.0, -0.0], [-1.0, 0.0, 1.0],
[-1.0, 0.0, -0.0]])
cart_pos_target = [[0., 0., 0.], [2.025, 2.025, 0.],
[0., -2.025, 2.025], [2.025, 0., 2.025],
[-2.025, 2.025, 0.], [-2.025, 0., 2.025],
[0., 2.025, 2.025], [-2.025, -2.025, 0.],
[0., 2.025, -2.025], [-2.025, 0., -2.025],
[2.025, -2.025, 0.], [2.025, 0., -2.025],
[0., -2.025, -2.025]]
# Transform to cartesian
cart_pos_predicted = []
for fractional in frac_pos:
cart_pos_predicted.append(
fractional_to_cartesian(structure, fractional))
# Test if predicted cartesian positions are equal to target
for target, predicted in zip(cart_pos_target, cart_pos_predicted):
np.testing.assert_almost_equal(target, predicted)
def test_get_permutation(self):
"""Tests the get_permutation function."""
value = ['a', 'b', 'c']
target = ['a', 'b', 'c']
permutation = [0, 1, 2]
self.assertEqual(target, get_permutation(value, permutation))
value = ['a', 'b', 'c']
target = ['a', 'c', 'b']
permutation = [0, 2, 1]
self.assertEqual(target, get_permutation(value, permutation))
value = [0, 3, 'c']
target = [3, 'c', 0]
permutation = [1, 2, 0]
self.assertEqual(target, get_permutation(value, permutation))
# Error on permutation list too short
with self.assertRaises(Exception):
get_permutation(value, [0, 1])
# Error on permutation list not unique values
with self.assertRaises(Exception):
get_permutation(value, [0, 1, 1])
# Error on permutation list going out of range
with self.assertRaises(IndexError):
get_permutation(value, [0, 1, 3])
def test_ase_atoms_to_spglib_cell(self):
"""
Tests that function returns the right tuple from the provided ASE
Atoms object.
"""
structure = bulk('Al').repeat(3)
structure[1].symbol = 'Ag'
cell, positions, species \
= ase_atoms_to_spglib_cell(self.structure)
self.assertTrue((cell == self.structure.get_cell()).all())
self.assertTrue(
(positions == self.structure.get_scaled_positions()).all())
self.assertTrue((species == self.structure.get_atomic_numbers()).all())
def test_chemical_symbols_to_numbers(self):
"""Tests chemical_symbols_to_numbers method."""
symbols = ['Al', 'H', 'He']
expected_numbers = [13, 1, 2]
retval = chemical_symbols_to_numbers(symbols)
self.assertEqual(expected_numbers, retval)
def test_atomic_number_to_chemical_symbol(self):
"""Tests chemical_symbols_to_numbers method."""
numbers = [13, 1, 2]
expected_symbols = ['Al', 'H', 'He']
retval = atomic_number_to_chemical_symbol(numbers)
self.assertEqual(expected_symbols, retval)
def test_get_wyckoff_sites(self):
"""Tests get_wyckoff_sites method."""
# structures and reference data to test
structures, targetvals = [], []
structures.append(bulk('Po', crystalstructure='sc', a=4))
targetvals.append(['1a'])
structures.append(bulk('W', crystalstructure='bcc', a=4))
targetvals.append(['2a'])
structures.append(bulk('Al', crystalstructure='fcc', a=4))
targetvals.append(['4a'])
structures.append(bulk('Ti', crystalstructure='hcp', a=4, c=6))
targetvals.append(2 * ['2d'])
structures.append(bulk('SiC', crystalstructure='zincblende', a=4))
targetvals.append(['4a', '4d'])
structures.append(bulk('NaCl', crystalstructure='rocksalt', a=4))
targetvals.append(['4a', '4b'])
structures.append(bulk('ZnO', crystalstructure='wurtzite', a=4, c=5))
targetvals.append(4 * ['2b'])
structures.append(bulk('Al', crystalstructure='fcc', a=4, cubic=True))
targetvals.append(4 * ['4a'])
structures.append(bulk('Al').repeat(2))
targetvals.append(8 * ['4a'])
structures.append(bulk('Ti').repeat((3, 2, 1)))
targetvals.append(12 * ['2d'])
structure = bulk('Al').repeat(2)
structure[0].position += [0, 0, 0.1]
structures.append(structure)
targetvals.append(['2a', '4b', '8c', '8c', '8c', '8c', '4b', '2a'])
for structure, targetval in zip(structures, targetvals):
retval = get_wyckoff_sites(structure)
self.assertEqual(targetval, retval)
structure = bulk('GaAs', crystalstructure='zincblende',
a=3.0).repeat(2)
structure.set_chemical_symbols([
'Ga', 'As', 'Al', 'As', 'Ga', 'As', 'Al', 'As', 'Ga', 'As', 'Ga',
'As', 'Al', 'As', 'Ga', 'As'
])
retval = get_wyckoff_sites(structure)
targetval = [
'8g', '8i', '4e', '8i', '8g', '8i', '2c', '8i', '2d', '8i', '8g',
'8i', '4e', '8i', '8g', '8i'
]
self.assertEqual(targetval, retval)
retval = get_wyckoff_sites(structure,
map_occupations=[['Ga', 'Al'], ['As']])
targetval = 8 * ['4a', '4c']
self.assertEqual(targetval, retval)
retval = get_wyckoff_sites(structure, map_occupations=[])
targetval = len(structure) * ['8a']
self.assertEqual(targetval, retval)
def calculate(self,
atoms=None,
properties=["energy"],
system_changes=all_changes):
Calculator.calculate(self, atoms, properties, system_changes)
image = atoms
params_dict = self.params
chemical_symbols = np.array(image.get_chemical_symbols())
params = []
for element in chemical_symbols:
re = params_dict[element]["re"]
D = params_dict[element]["De"]
# sig calculated from pubs.acs.org/doi/pdf/10.1021/acs.jpca.7b11252
sig = re - np.log(2) / params_dict[element]["a"]
params.append(np.array([[re, D, sig]]))
params = np.vstack(np.array(params))
n = NeighborList(
cutoffs=[self.cutoff / 2.0] * len(image),
self_interaction=False,
primitive=NewPrimitiveNeighborList,
)
n.update(image)
image_neighbors = [
n.get_neighbors(index) for index in range(len(image))
]
natoms = len(image)
positions = image.positions
cell = image.cell
energy = 0.0
forces = np.zeros((natoms, 3))
for a1 in range(natoms):
re_1 = params[a1][0]
D_1 = np.abs(params[a1][1])
sig_1 = params[a1][2]
neighbors, offsets = image_neighbors[a1]
cells = np.dot(offsets, cell)
d = positions[neighbors] + cells - positions[a1]
re_n = params[neighbors][:, 0]
D_n = params[neighbors][:, 1]
sig_n = params[neighbors][:, 2]
if self.combo == "mean":
D = np.sqrt(D_1 * D_n)
sig = (sig_1 + sig_n) / 2
re = (re_1 + re_n) / 2
elif self.combo == "yang":
D = (2 * D_1 * D_n) / (D_1 + D_n)
sig = (sig_1 * sig_n) * (sig_1 + sig_n) / (sig_1**2 + sig_n**2)
re = (re_1 * re_n) * (re_1 + re_n) / (re_1**2 + re_n**2)
r = np.sqrt((d**2).sum(1))
r_star = r / sig
re_star = re / sig
C = np.log(2) / (re_star - 1)
atom_energy = D * (np.exp(-2 * C * (r_star - re_star)) -
2 * np.exp(-C * (r_star - re_star)))
energy += atom_energy.sum()
f = ((2 * D * C / sig) * (1 / r) *
(np.exp(-2 * C * (r_star - re_star)) -
np.exp(-C * (r_star - re_star))))[:, np.newaxis] * d
forces[a1] -= f.sum(axis=0)
for a2, f2 in zip(neighbors, f):
forces[a2] += f2
self.results["energy"] = energy
self.results["forces"] = forces
class TorchAtoms(Atoms):
def __init__(self,
ase_atoms=None,
energy=None,
forces=None,
cutoff=None,
descriptors=[],
group=None,
ranks=None,
**kwargs):
super().__init__(**kwargs)
if ase_atoms:
self.__dict__ = ase_atoms.__dict__
# ------------------------------- ----------
if type(ranks) == Distributer:
self.ranks = None
ranks(self)
else:
self.ranks = ranks
if group is not None:
self.attach_process_group(group)
else:
self.is_distributed = False
self.cutoff = cutoff
self.descriptors = descriptors
self.changes = AtomsChanges(self)
if cutoff is not None:
self.build_nl(cutoff)
self.update(forced=True)
# ------------------------------------------
try:
self.target_energy = as_tensor(energy)
self.target_forces = as_tensor(forces)
except RuntimeError:
if ase_atoms is not None and ase_atoms.get_calculator(
) is not None:
if 'energy' in ase_atoms.calc.results:
self.target_energy = as_tensor(
ase_atoms.get_potential_energy())
if 'forces' in ase_atoms.calc.results:
self.target_forces = as_tensor(ase_atoms.get_forces())
def set_targets(self):
self.target_energy = as_tensor(self.get_potential_energy())
self.target_forces = as_tensor(self.get_forces())
def attach_process_group(self, group):
self.process_group = group
self.is_distributed = True
self.index_distribute()
def index_distribute(self, randomize=True):
if self.is_distributed:
rank = torch.distributed.get_rank(group=self.process_group)
if self.ranks:
self.indices = []
for i, j in enumerate(self.ranks):
if j == rank:
self.indices.append(i)
else:
workers = torch.distributed.get_world_size(
group=self.process_group)
indices = balance_work(self.natoms, workers)
if randomize:
# reproducibility issue: rnd sequence becomes workers dependent
# w = np.random.permutation(workers)
w = (np.arange(workers) +
np.random.randint(1024)) % workers
j = np.random.permutation(self.natoms)
self.indices = j[range(*indices[w[rank]])].tolist()
else:
self.indices = range(*indices[rank])
else:
self.indices = range(self.natoms)
def detach_process_group(self):
del self.process_group
self.is_distributed = False
self.index_distribute()
def build_nl(self, rc):
self.nl = NeighborList(self.natoms * [rc / 2],
skin=0.0,
self_interaction=False,
bothways=True)
self.cutoff = rc
self.xyz = torch.from_numpy(self.positions)
try:
self.lll = torch.from_numpy(self.cell)
except TypeError:
self.lll = torch.from_numpy(self.cell.array)
# distributed setup
self.index_distribute()
def local(self, a, stage=True, dont_save_grads=True, detach=False):
n, off = self.nl.get_neighbors(a)
cells = (from_numpy(off[..., None].astype(np.float)) *
self.lll).sum(dim=1)
r = self.xyz[n] - self.xyz[a] + cells
if detach:
r = r.detach()
loc = Local(a,
n,
self.numbers[a],
self.numbers[n],
r,
off,
self.descriptors if stage else [],
dont_save_grads=dont_save_grads)
loc.natoms = self.natoms
return loc
def update(self,
cutoff=None,
descriptors=None,
forced=False,
build_locals=True,
stage=True,
posgrad=False,
cellgrad=False,
dont_save_grads=False):
if cutoff or self.changes.numbers:
self.build_nl(cutoff if cutoff else self.cutoff)
forced = True
if descriptors:
self.descriptors = descriptors
forced = True
if forced or self.changes.atoms:
self.nl.update(self)
self.xyz.requires_grad = posgrad
self.lll.requires_grad = cellgrad
self.loc = [
self.local(a, stage=stage, dont_save_grads=dont_save_grads)
for a in self.indices
] if build_locals else None
self.changes.update_references()
def stage(self, descriptors=None, dont_save_grads=True):
descs = iterable(descriptors) if descriptors else self.descriptors
for loc in self.loc:
loc.stage(descs, dont_save_grads=dont_save_grads)
def set_descriptors(self, descriptors, stage=True, dont_save_grads=True):
self.descriptors = [d for d in iterable(descriptors)]
if stage:
self.stage(dont_save_grads=dont_save_grads)
def add_descriptors(self, descriptors, stage=True, dont_save_grads=True):
self.descriptors = [d for d in self.descriptors] + \
[d for d in iterable(descriptors)]
names = [d.name for d in self.descriptors]
if len(set(names)) != len(self.descriptors):
raise RuntimeError(
f'two or more descriptors have the same names: {names}')
if stage:
self.stage(iterable(descriptors), dont_save_grads=dont_save_grads)
@property
def natoms(self):
return self.get_global_number_of_atoms()
@property
def tnumbers(self):
return torch.from_numpy(self.numbers)
@property
def numbers_set(self):
return np.unique(self.numbers).tolist()
@property
def tpbc(self):
return torch.from_numpy(self.pbc)
def includes_species(self, species):
return any([a in iterable(species) for a in self.numbers_set])
def cat(self, attr):
"""__getattr__ -> renamed to cat"""
try:
return torch.cat([env.__dict__[attr] for env in self.loc])
except KeyError:
raise AttributeError()
def __getitem__(self, k):
"""This is a overloads the behavior of ase.Atoms."""
return self.loc[k]
def __iter__(self):
"""This is a overloads the behavior of ase.Atoms."""
for env in self.loc:
yield env
def first_of_each_atom_type(atoms):
indices = []
unique = []
for i, a in enumerate(atoms.numbers):
if a not in unique:
unique += [a]
indices += [i]
return indices
def __eq__(self, other): # Note: descriptors are excluded
if other.__class__ == Local:
return False
elif self.natoms != other.natoms:
return False
elif (self.pbc != other.pbc).any():
return False
elif not self.lll.allclose(other.lll):
return False
elif (self.numbers != other.numbers).any():
return False
elif not self.xyz.allclose(other.xyz):
return False
else:
return True
def copy(self, update=True, group=True):
new = TorchAtoms(positions=self.positions.copy(),
cell=self.cell.copy(),
numbers=self.numbers.copy(),
pbc=self.pbc.copy(),
ranks=self.ranks)
if group and self.is_distributed:
new.attach_process_group(self.process_group)
assert new.indices == self.indices # TODO: ignore?
if update:
new.update(cutoff=self.cutoff, descriptors=self.descriptors)
vel = self.get_velocities()
if vel is not None:
new.set_velocities(vel.copy())
return new
def set_cell(self, *args, **kwargs):
super().set_cell(*args, **kwargs)
try:
self.lll = torch.from_numpy(self.cell)
except TypeError:
self.lll = torch.from_numpy(self.cell.array)
def set_positions(self, *args, **kwargs):
super().set_positions(*args, **kwargs)
self.xyz = torch.from_numpy(self.positions)
def as_ase(self):
atoms = Atoms(positions=self.positions,
cell=self.cell,
pbc=self.pbc,
numbers=self.numbers)
atoms.calc = self.calc # DONE: e, f
if atoms.calc is not None:
atoms.calc.atoms = atoms
vel = self.get_velocities()
if vel is not None:
atoms.set_velocities(vel)
return atoms
def as_local(self):
""" As the inverse of Local.as_atoms """
# positions[0] should to be [0, 0, 0]
r = torch.as_tensor(self.positions[1:])
#a, b = np.broadcast_arrays(self.numbers[0], self.numbers[1:])
a, b = self.numbers[0], self.numbers[1:]
_i = np.arange(self.natoms)
i, j = np.broadcast_arrays(_i[0], _i[1:])
loc = Local(i, j, a, b, r)
if 'target_energy' in self.__dict__:
loc.target_energy = self.target_energy
return loc
def shake(self, beta=0.05, update=True):
trans = np.random.laplace(0., beta, size=self.positions.shape)
self.translate(trans)
if update:
self.update()
def single_point(self):
results = {}
for q in ['energy', 'forces', 'stress', 'xx']:
try:
results[q] = self.calc.results[q]
except KeyError:
pass
self.set_calculator(SinglePointCalculator(self, **results))
def detached(self, set_targets=True):
results = {}
for q in ['energy', 'forces', 'stress', 'xx']:
try:
results[q] = self.calc.results[q]
except KeyError:
pass
new = self.copy()
new.set_calculator(SinglePointCalculator(new, **results))
if set_targets:
new.set_targets()
return new
def pickle_locals(self, folder='atoms'):
mkdir_p(folder)
for loc in self.loc:
f = os.path.join(folder, f'loc_{loc.index}.pckl')
torch.save(loc, f)
def pickles(self, folder='atoms'):
return [
torch.load(os.path.join(folder, f'loc_{i}.pckl'))
for i in range(self.natoms)
]
def gathered(self, folder='atoms'):
if self.is_distributed and len(self.loc) < self.natoms:
self.pickle_locals(folder=folder)
dist.barrier(self.process_group)
loc = self.pickles()
else:
loc = self.loc
return loc
def gather_(self, folder='atoms'):
self.loc = self.gathered(folder=folder)
self.detach_process_group()
def distribute_(self, group):
self.attach_process_group(group)
self.loc = [self.loc[i] for i in self.indices]
def counts(self, total=True):
c = Counter()
if total:
for number in self.numbers.tolist():
c[number] += 1
else:
for loc in self.loc:
c[loc.number] += 1
return c
def surface_coordination(atoms, cutoff=None, verbose=True):
'''
This function allows to extract the following data from the
supplied Atoms object in the form of a dictionary:
Per atom:
- number of neighbouring atoms of specific chemical symbol
Per atomic layer (based on tag):
- average coordination number for all M-M combinations of all chemical species,
e.g. for CuAu alloy slab an average number of Cu-Cu, Cu-Au, Au-Cu and Au-Au
bonds with surrounding atoms i.e. Cu-Cu_neighbors_per_layer etc.
- concentration of atoms per layer
Parameters:
atoms: Atoms object
Surface slab containing tagged atomic layers
e.g. using carmm.build.neb.symmetry.sort_z
cutoff: list of floats or None
Bond length cutoff distance in Angstrom can be set for each atom individually
The list must contain exactly len(atoms) floats. If None, natural_cutoffs
are used by default.
verbose: boolean
If True, analysed data that is contained in the dictionary will be printed
as a table
TODO: make table neater
Returns:
dict_CN, dict_surf_CN
TODO: proper description of dictionary structure, writing csv files'''
from ase.neighborlist import natural_cutoffs, NeighborList
import numpy as np
from collections import Counter
from itertools import product
dict_CN = {}
if not cutoff:
# Choose a cutoff to determine max bond distance
cutoff = natural_cutoffs(atoms)
if verbose:
print("Default bond cutoffs selected:", set([(atoms[i].symbol, cutoff[i]) for i in range(len(atoms))]))
# Create a symbols set based on all species present in the atoms
symbols_set = sorted(list(set(atoms.symbols)))
for l in set(atoms.get_tags()):
index= [i.index for i in atoms if i.tag == l]
for i in index:
nl = NeighborList(cutoff, self_interaction=False, bothways=True)
nl.update(atoms)
indices, offsets = nl.get_neighbors(i)
# avoid duplicate atomic indices
indices_no_self = np.array(list(set([j for j in indices])))
cn_numbers = Counter(atoms[indices_no_self].symbols)
# create a dictionary of relevant values for cn calculations
dict_CN[i] = {"symbol":atoms[i].symbol, 'index':i, "layer":l}
for k in symbols_set:
dict_CN[i].update({k+"_neighbors":cn_numbers[k]})
# check all combinations of atomic symbols
pr = product(symbols_set, repeat=2)
dict_surf_CN= {}
for layer in set(atoms.get_tags()):
dict_surf_CN[layer] = {}
dict_surf_CN[layer].update({"layer":layer})
# extract data for all combinations of neighbors and put at the end of the dictionary
for p in product(symbols_set, repeat=2):
M_M_cn = [dict_CN[x][p[0] + "_neighbors"] for x in dict_CN if\
dict_CN[x]["layer"] == layer and dict_CN[x]['symbol'] == p[1]]
if not M_M_cn == []:
M_M_avg_cn = np.average(M_M_cn)
else:
M_M_avg_cn = "N/A"
dict_surf_CN[layer].update({p[0] + "_neighboring_w_" + p[1]: M_M_avg_cn})
# Check concentrations of atoms per layer
for symbol in symbols_set:
atoms_per_layer = len([x for x in dict_CN if dict_CN[x]["layer"] == layer])
if atoms_per_layer > 0:
symbol_count_per_layer = len([symbol for x in dict_CN if dict_CN[x]["layer"] == layer and dict_CN[x]['symbol'] == symbol])
symbol_concentration_per_layer = symbol_count_per_layer / atoms_per_layer
else:
symbol_concentration_per_layer = 0
dict_surf_CN[layer].update({symbol+"_concentration_per_layer":symbol_concentration_per_layer})
# Preparation for verbose
cn_layer_list_dict = [dict_surf_CN[i] for i in range(len(dict_surf_CN))]
cn_layer_dict_keys = [dict_surf_CN[i].keys() for i in range(len(dict_surf_CN))][0]
# Optional text output
if verbose:
print([key for key in cn_layer_dict_keys])
for i in range(len(dict_surf_CN)):
print([cn_layer_list_dict[i][key] for key in cn_layer_dict_keys])
return dict_CN, dict_surf_CN
class EAM(Calculator):
r"""
EAM Interface Documentation
Introduction
============
The Embedded Atom Method (EAM) [1]_ is a classical potential which is
good for modelling metals, particularly fcc materials. Because it is
an equiaxial potential the EAM does not model directional bonds
well. However, the Angular Dependent Potential (ADP) [2]_ which is an
extended version of EAM is able to model directional bonds and is also
included in the EAM calculator.
Generally all that is required to use this calculator is to supply a
potential file or as a set of functions that describe the potential.
The files containing the potentials for this calculator are not
included but many suitable potentials can be downloaded from The
Interatomic Potentials Repository Project at
https://www.ctcms.nist.gov/potentials/
Theory
======
A single element EAM potential is defined by three functions: the
embedded energy, electron density and the pair potential. A two
element alloy contains the individual three functions for each element
plus cross pair interactions. The ADP potential has two additional
sets of data to define the dipole and quadrupole directional terms for
each alloy and their cross interactions.
The total energy `E_{\rm tot}` of an arbitrary arrangement of atoms is
given by the EAM potential as
.. math::
E_\text{tot} = \sum_i F(\bar\rho_i) + \frac{1}{2}\sum_{i\ne j} \phi(r_{ij})
and
.. math::
\bar\rho_i = \sum_j \rho(r_{ij})
where `F` is an embedding function, namely the energy to embed an atom `i` in
the combined electron density `\bar\rho_i` which is contributed from
each of its neighbouring atoms `j` by an amount `\rho(r_{ij})`,
`\phi(r_{ij})` is the pair potential function representing the energy
in bond `ij` which is due to the short-range electro-static
interaction between atoms, and `r_{ij}` is the distance between an
atom and its neighbour for that bond.
The ADP potential is defined as
.. math::
E_\text{tot} = \sum_i F(\bar\rho_i) + \frac{1}{2}\sum_{i\ne j} \phi(r_{ij})
+ \frac{1}{2} \sum_{i,\alpha} (\mu_i^\alpha)^2
+ \frac{1}{2} \sum_{i,\alpha,\beta} (\lambda_i^{\alpha\beta})^2
- \frac{1}{6} \sum_i \nu_i^2
where `\mu_i^\alpha` is the dipole vector, `\lambda_i^{\alpha\beta}`
is the quadrupole tensor and `\nu_i` is the trace of
`\lambda_i^{\alpha\beta}`.
The fs potential is defined as
.. math::
E_i = F_\alpha (\sum_{j\neq i} \rho_{\alpha \beta}(r_{ij}))
+ \frac{1}{2}\sum_{j\neq i}\phi_{\alpha \beta}(r_{ij})
where `\alpha` and `\beta` are element types of atoms. This form is similar to
original EAM formula above, except that `\rho` and `\phi` are determined
by element types.
Running the Calculator
======================
EAM calculates the cohesive atom energy and forces. Internally the
potential functions are defined by splines which may be directly
supplied or created by reading the spline points from a data file from
which a spline function is created. The LAMMPS compatible ``.alloy``, ``.fs``
and ``.adp`` formats are supported. The LAMMPS ``.eam`` format is
slightly different from the ``.alloy`` format and is currently not
supported.
For example::
from ase.calculators.eam import EAM
mishin = EAM(potential='Al99.eam.alloy')
mishin.write_potential('new.eam.alloy')
mishin.plot()
slab.set_calculator(mishin)
slab.get_potential_energy()
slab.get_forces()
The breakdown of energy contribution from the indvidual components are
stored in the calculator instance ``.results['energy_components']``
Arguments
=========
========================= ====================================================
Keyword Description
========================= ====================================================
``potential`` file of potential in ``.eam``, ``.alloy``, ``.adp`` or ``.fs``
format or file object (This is generally all you need to supply).
In case of file object the ``form`` argument is required
``elements[N]`` array of N element abbreviations
``embedded_energy[N]`` arrays of embedded energy functions
``electron_density[N]`` arrays of electron density functions
``phi[N,N]`` arrays of pair potential functions
``d_embedded_energy[N]`` arrays of derivative embedded energy functions
``d_electron_density[N]`` arrays of derivative electron density functions
``d_phi[N,N]`` arrays of derivative pair potentials functions
``d[N,N], q[N,N]`` ADP dipole and quadrupole function
``d_d[N,N], d_q[N,N]`` ADP dipole and quadrupole derivative functions
``skin`` skin distance passed to NeighborList(). If no atom
has moved more than the skin-distance since the last
call to the ``update()`` method then the neighbor
list can be reused. Defaults to 1.0.
``form`` the form of the potential ``eam``, ``alloy``, ``adp`` or
``fs``. This will be determined from the file suffix
or must be set if using equations or file object
========================= ====================================================
Additional parameters for writing potential files
=================================================
The following parameters are only required for writing a potential in
``.alloy``, ``.adp`` or ``fs`` format file.
========================= ====================================================
Keyword Description
========================= ====================================================
``header`` Three line text header. Default is standard message.
``Z[N]`` Array of atomic number of each element
``mass[N]`` Atomic mass of each element
``a[N]`` Array of lattice parameters for each element
``lattice[N]`` Lattice type
``nrho`` No. of rho samples along embedded energy curve
``drho`` Increment for sampling density
``nr`` No. of radial points along density and pair
potential curves
``dr`` Increment for sampling radius
========================= ====================================================
Special features
================
``.plot()``
Plots the individual functions. This may be called from multiple EAM
potentials to compare the shape of the individual curves. This
function requires the installation of the Matplotlib libraries.
Notes/Issues
=============
* Although currently not fast, this calculator can be good for trying
small calculations or for creating new potentials by matching baseline
data such as from DFT results. The format for these potentials is
compatible with LAMMPS_ and so can be used either directly by LAMMPS or
with the ASE LAMMPS calculator interface.
* Supported formats are the LAMMPS_ ``.alloy`` and ``.adp``. The
``.eam`` format is currently not supported. The form of the
potential will be determined from the file suffix.
* Any supplied values will override values read from the file.
* The derivative functions, if supplied, are only used to calculate
forces.
* There is a bug in early versions of scipy that will cause eam.py to
crash when trying to evaluate splines of a potential with one
neighbor such as caused by evaluating a dimer.
.. _LAMMPS: http://lammps.sandia.gov/
.. [1] M.S. Daw and M.I. Baskes, Phys. Rev. Letters 50 (1983)
1285.
.. [2] Y. Mishin, M.J. Mehl, and D.A. Papaconstantopoulos,
Acta Materialia 53 2005 4029--4041.
End EAM Interface Documentation
"""
implemented_properties = ['energy', 'forces']
default_parameters = dict(skin=1.0,
potential=None,
header=[
b'EAM/ADP potential file\n',
b'Generated from eam.py\n', b'blank\n'
])
def __init__(self,
restart=None,
ignore_bad_restart_file=False,
label=os.curdir,
atoms=None,
form=None,
**kwargs):
self.form = form
if 'potential' in kwargs:
self.read_potential(kwargs['potential'])
Calculator.__init__(self, restart, ignore_bad_restart_file, label,
atoms, **kwargs)
valid_args = (
'potential',
'elements',
'header',
'drho',
'dr',
'cutoff',
'atomic_number',
'mass',
'a',
'lattice',
'embedded_energy',
'electron_density',
'phi',
# derivatives
'd_embedded_energy',
'd_electron_density',
'd_phi',
'd',
'q',
'd_d',
'd_q', # adp terms
'skin',
'Z',
'nr',
'nrho',
'mass')
# set any additional keyword arguments
for arg, val in self.parameters.items():
if arg in valid_args:
setattr(self, arg, val)
else:
raise RuntimeError('unknown keyword arg "%s" : not in %s' %
(arg, valid_args))
def set_form(self, fileobj):
"""set the form variable based on the file name suffix"""
extension = os.path.splitext(fileobj)[1]
if extension == '.eam':
self.form = 'eam'
elif extension == '.alloy':
self.form = 'alloy'
elif extension == '.adp':
self.form = 'adp'
elif extension == '.fs':
self.form = 'fs'
else:
raise RuntimeError('unknown file extension type: %s' % extension)
def read_potential(self, fileobj):
"""Reads a LAMMPS EAM file in alloy or adp format
and creates the interpolation functions from the data
"""
if isinstance(fileobj, basestring):
f = open(fileobj)
if self.form is None:
self.set_form(fileobj)
else:
f = fileobj
def lines_to_list(lines):
"""Make the data one long line so as not to care how its formatted
"""
data = []
for line in lines:
data.extend(line.split())
return data
lines = f.readlines()
if self.form == 'eam': # single element eam file (aka funcfl)
self.header = lines[:1]
data = lines_to_list(lines[1:])
# eam form is just like an alloy form for one element
self.Nelements = 1
self.Z = np.array([data[0]], dtype=int)
self.mass = np.array([data[1]])
self.a = np.array([data[2]])
self.lattice = [data[3]]
self.nrho = int(data[4])
self.drho = float(data[5])
self.nr = int(data[6])
self.dr = float(data[7])
self.cutoff = float(data[8])
n = 9 + self.nrho
self.embedded_data = np.array([np.float_(data[9:n])])
self.rphi_data = np.zeros(
[self.Nelements, self.Nelements, self.nr])
effective_charge = np.float_(data[n:n + self.nr])
# convert effective charges to rphi according to
# http://lammps.sandia.gov/doc/pair_eam.html
self.rphi_data[0, 0] = Bohr * Hartree * (effective_charge**2)
self.density_data = np.array(
[np.float_(data[n + self.nr:n + 2 * self.nr])])
elif self.form in ['alloy', 'adq']:
self.header = lines[:3]
i = 3
data = lines_to_list(lines[i:])
self.Nelements = int(data[0])
d = 1
self.elements = data[d:d + self.Nelements]
d += self.Nelements
self.nrho = int(data[d])
self.drho = float(data[d + 1])
self.nr = int(data[d + 2])
self.dr = float(data[d + 3])
self.cutoff = float(data[d + 4])
self.embedded_data = np.zeros([self.Nelements, self.nrho])
self.density_data = np.zeros([self.Nelements, self.nr])
self.Z = np.zeros([self.Nelements], dtype=int)
self.mass = np.zeros([self.Nelements])
self.a = np.zeros([self.Nelements])
self.lattice = []
d += 5
# reads in the part of the eam file for each element
for elem in range(self.Nelements):
self.Z[elem] = int(data[d])
self.mass[elem] = float(data[d + 1])
self.a[elem] = float(data[d + 2])
self.lattice.append(data[d + 3])
d += 4
self.embedded_data[elem] = np.float_(data[d:(d + self.nrho)])
d += self.nrho
self.density_data[elem] = np.float_(data[d:(d + self.nr)])
d += self.nr
# reads in the r*phi data for each interaction between elements
self.rphi_data = np.zeros(
[self.Nelements, self.Nelements, self.nr])
for i in range(self.Nelements):
for j in range(i + 1):
self.rphi_data[j, i] = np.float_(data[d:(d + self.nr)])
d += self.nr
elif self.form == 'fs':
self.header = lines[:3]
i = 3
data = lines_to_list(lines[i:])
self.Nelements = int(data[0])
d = 1
self.elements = data[d:d + self.Nelements]
d += self.Nelements
self.nrho = int(data[d])
self.drho = float(data[d + 1])
self.nr = int(data[d + 2])
self.dr = float(data[d + 3])
self.cutoff = float(data[d + 4])
self.embedded_data = np.zeros([self.Nelements, self.nrho])
self.density_data = np.zeros(
[self.Nelements, self.Nelements, self.nr])
self.Z = np.zeros([self.Nelements], dtype=int)
self.mass = np.zeros([self.Nelements])
self.a = np.zeros([self.Nelements])
self.lattice = []
d += 5
# reads in the part of the eam file for each element
for elem in range(self.Nelements):
self.Z[elem] = int(data[d])
self.mass[elem] = float(data[d + 1])
self.a[elem] = float(data[d + 2])
self.lattice.append(data[d + 3])
d += 4
self.embedded_data[elem] = np.float_(data[d:(d + self.nrho)])
d += self.nrho
self.density_data[elem, :, :] = np.float_(
data[d:(d + self.nr * self.Nelements)]).reshape(
[self.Nelements, self.nr])
d += self.nr * self.Nelements
# reads in the r*phi data for each interaction between elements
self.rphi_data = np.zeros(
[self.Nelements, self.Nelements, self.nr])
for i in range(self.Nelements):
for j in range(i + 1):
self.rphi_data[j, i] = np.float_(data[d:(d + self.nr)])
d += self.nr
self.r = np.arange(0, self.nr) * self.dr
self.rho = np.arange(0, self.nrho) * self.drho
# choose the set_splines method according to the type
if self.form == 'fs':
self.set_fs_splines()
else:
self.set_splines()
if (self.form == 'adp'):
self.read_adp_data(data, d)
self.set_adp_splines()
def set_splines(self):
# this section turns the file data into three functions (and
# derivative functions) that define the potential
self.embedded_energy = np.empty(self.Nelements, object)
self.electron_density = np.empty(self.Nelements, object)
self.d_embedded_energy = np.empty(self.Nelements, object)
self.d_electron_density = np.empty(self.Nelements, object)
for i in range(self.Nelements):
self.embedded_energy[i] = spline(self.rho,
self.embedded_data[i],
k=3)
self.electron_density[i] = spline(self.r,
self.density_data[i],
k=3)
self.d_embedded_energy[i] = self.deriv(self.embedded_energy[i])
self.d_electron_density[i] = self.deriv(self.electron_density[i])
self.phi = np.empty([self.Nelements, self.Nelements], object)
self.d_phi = np.empty([self.Nelements, self.Nelements], object)
# ignore the first point of the phi data because it is forced
# to go through zero due to the r*phi format in alloy and adp
for i in range(self.Nelements):
for j in range(i, self.Nelements):
self.phi[i, j] = spline(self.r[1:],
self.rphi_data[i, j][1:] / self.r[1:],
k=3)
self.d_phi[i, j] = self.deriv(self.phi[i, j])
if j != i:
self.phi[j, i] = self.phi[i, j]
self.d_phi[j, i] = self.d_phi[i, j]
def set_fs_splines(self):
self.embedded_energy = np.empty(self.Nelements, object)
self.electron_density = np.empty([self.Nelements, self.Nelements],
object)
self.d_embedded_energy = np.empty(self.Nelements, object)
self.d_electron_density = np.empty([self.Nelements, self.Nelements],
object)
for i in range(self.Nelements):
self.embedded_energy[i] = spline(self.rho,
self.embedded_data[i],
k=3)
self.d_embedded_energy[i] = self.deriv(self.embedded_energy[i])
for j in range(self.Nelements):
self.electron_density[i, j] = spline(self.r,
self.density_data[i, j],
k=3)
self.d_electron_density[i, j] = self.deriv(
self.electron_density[i, j])
self.phi = np.empty([self.Nelements, self.Nelements], object)
self.d_phi = np.empty([self.Nelements, self.Nelements], object)
for i in range(self.Nelements):
for j in range(i, self.Nelements):
self.phi[i, j] = spline(self.r[1:],
self.rphi_data[i, j][1:] / self.r[1:],
k=3)
self.d_phi[i, j] = self.deriv(self.phi[i, j])
if j != i:
self.phi[j, i] = self.phi[i, j]
self.d_phi[j, i] = self.d_phi[i, j]
def set_adp_splines(self):
self.d = np.empty([self.Nelements, self.Nelements], object)
self.d_d = np.empty([self.Nelements, self.Nelements], object)
self.q = np.empty([self.Nelements, self.Nelements], object)
self.d_q = np.empty([self.Nelements, self.Nelements], object)
for i in range(self.Nelements):
for j in range(i, self.Nelements):
self.d[i, j] = spline(self.r[1:], self.d_data[i, j][1:], k=3)
self.d_d[i, j] = self.deriv(self.d[i, j])
self.q[i, j] = spline(self.r[1:], self.q_data[i, j][1:], k=3)
self.d_q[i, j] = self.deriv(self.q[i, j])
# make symmetrical
if j != i:
self.d[j, i] = self.d[i, j]
self.d_d[j, i] = self.d_d[i, j]
self.q[j, i] = self.q[i, j]
self.d_q[j, i] = self.d_q[i, j]
def read_adp_data(self, data, d):
"""read in the extra adp data from the potential file"""
self.d_data = np.zeros([self.Nelements, self.Nelements, self.nr])
# should be non symmetrical combinations of 2
for i in range(self.Nelements):
for j in range(i + 1):
self.d_data[j, i] = data[d:d + self.nr]
d += self.nr
self.q_data = np.zeros([self.Nelements, self.Nelements, self.nr])
# should be non symmetrical combinations of 2
for i in range(self.Nelements):
for j in range(i + 1):
self.q_data[j, i] = data[d:d + self.nr]
d += self.nr
def write_potential(self, filename, nc=1, numformat='%.8e'):
"""Writes out the potential in the format given by the form
variable to 'filename' with a data format that is nc columns
wide. Note: array lengths need to be an exact multiple of nc
"""
f = open(filename, 'wb')
assert self.nr % nc == 0
assert self.nrho % nc == 0
for line in self.header:
f.write(line)
f.write('{0} '.format(self.Nelements).encode())
f.write(' '.join(self.elements).encode() + b'\n')
f.write(
('%d %f %d %f %f \n' %
(self.nrho, self.drho, self.nr, self.dr, self.cutoff)).encode())
# start of each section for each element
# rs = np.linspace(0, self.nr * self.dr, self.nr)
# rhos = np.linspace(0, self.nrho * self.drho, self.nrho)
rs = np.arange(0, self.nr) * self.dr
rhos = np.arange(0, self.nrho) * self.drho
for i in range(self.Nelements):
f.write(('%d %f %f %s\n' % (self.Z[i], self.mass[i], self.a[i],
str(self.lattice[i]))).encode())
np.savetxt(f,
self.embedded_energy[i](rhos).reshape(
self.nrho // nc, nc),
fmt=nc * [numformat])
if self.form == 'fs':
for j in range(self.Nelements):
np.savetxt(f,
self.electron_density[i, j](rs).reshape(
self.nr // nc, nc),
fmt=nc * [numformat])
else:
np.savetxt(f,
self.electron_density[i](rs).reshape(
self.nr // nc, nc),
fmt=nc * [numformat])
# write out the pair potentials in Lammps DYNAMO setfl format
# as r*phi for alloy format
for i in range(self.Nelements):
for j in range(i, self.Nelements):
np.savetxt(f, (rs * self.phi[i, j](rs)).reshape(
self.nr // nc, nc),
fmt=nc * [numformat])
if self.form == 'adp':
# these are the u(r) or dipole values
for i in range(self.Nelements):
for j in range(i + 1):
np.savetxt(f, self.d_data[i, j])
# these are the w(r) or quadrupole values
for i in range(self.Nelements):
for j in range(i + 1):
np.savetxt(f, self.q_data[i, j])
f.close()
def update(self, atoms):
# check all the elements are available in the potential
self.Nelements = len(self.elements)
elements = np.unique(atoms.get_chemical_symbols())
unavailable = np.logical_not(
np.array([item in self.elements for item in elements]))
if np.any(unavailable):
raise RuntimeError('These elements are not in the potential: %s' %
elements[unavailable])
# cutoffs need to be a vector for NeighborList
cutoffs = self.cutoff * np.ones(len(atoms))
# convert the elements to an index of the position
# in the eam format
self.index = np.array(
[self.elements.index(el) for el in atoms.get_chemical_symbols()])
self.pbc = atoms.get_pbc()
# since we need the contribution of all neighbors to the
# local electron density we cannot just calculate and use
# one way neighbors
self.neighbors = NeighborList(cutoffs,
skin=self.parameters.skin,
self_interaction=False,
bothways=True)
self.neighbors.update(atoms)
def calculate(self,
atoms=None,
properties=['energy'],
system_changes=all_changes):
"""EAM Calculator
atoms: Atoms object
Contains positions, unit-cell, ...
properties: list of str
List of what needs to be calculated. Can be any combination
of 'energy', 'forces'
system_changes: list of str
List of what has changed since last calculation. Can be
any combination of these five: 'positions', 'numbers', 'cell',
'pbc', 'initial_charges' and 'initial_magmoms'.
"""
Calculator.calculate(self, atoms, properties, system_changes)
# we shouldn't really recalc if charges or magmos change
if len(system_changes) > 0: # something wrong with this way
self.update(self.atoms)
self.calculate_energy(self.atoms)
if 'forces' in properties:
self.calculate_forces(self.atoms)
# check we have all the properties requested
for property in properties:
if property not in self.results:
if property == 'energy':
self.calculate_energy(self.atoms)
if property == 'forces':
self.calculate_forces(self.atoms)
# we need to remember the previous state of parameters
# if 'potential' in parameter_changes and potential != None:
# self.read_potential(potential)
def calculate_energy(self, atoms):
"""Calculate the energy
the energy is made up of the ionic or pair interaction and
the embedding energy of each atom into the electron cloud
generated by its neighbors
"""
pair_energy = 0.0
embedding_energy = 0.0
mu_energy = 0.0
lam_energy = 0.0
trace_energy = 0.0
self.total_density = np.zeros(len(atoms))
if (self.form == 'adp'):
self.mu = np.zeros([len(atoms), 3])
self.lam = np.zeros([len(atoms), 3, 3])
for i in range(len(atoms)): # this is the atom to be embedded
neighbors, offsets = self.neighbors.get_neighbors(i)
offset = np.dot(offsets, atoms.get_cell())
rvec = (atoms.positions[neighbors] + offset - atoms.positions[i])
# calculate the distance to the nearest neighbors
r = np.sqrt(np.sum(np.square(rvec), axis=1)) # fast
# r = np.apply_along_axis(np.linalg.norm, 1, rvec) # sloow
nearest = np.arange(len(r))[r <= self.cutoff]
for j_index in range(self.Nelements):
use = self.index[neighbors[nearest]] == j_index
if not use.any():
continue
pair_energy += np.sum(self.phi[self.index[i], j_index](
r[nearest][use])) / 2.
if self.form == 'fs':
density = np.sum(
self.electron_density[j_index,
self.index[i]](r[nearest][use]))
else:
density = np.sum(self.electron_density[j_index](
r[nearest][use]))
self.total_density[i] += density
if self.form == 'adp':
self.mu[i] += self.adp_dipole(
r[nearest][use], rvec[nearest][use],
self.d[self.index[i], j_index])
self.lam[i] += self.adp_quadrupole(
r[nearest][use], rvec[nearest][use],
self.q[self.index[i], j_index])
# add in the electron embedding energy
embedding_energy += self.embedded_energy[self.index[i]](
self.total_density[i])
components = dict(pair=pair_energy, embedding=embedding_energy)
if self.form == 'adp':
mu_energy += np.sum(self.mu**2) / 2.
lam_energy += np.sum(self.lam**2) / 2.
for i in range(len(atoms)): # this is the atom to be embedded
trace_energy -= np.sum(self.lam[i].trace()**2) / 6.
adp_result = dict(adp_mu=mu_energy,
adp_lam=lam_energy,
adp_trace=trace_energy)
components.update(adp_result)
self.positions = atoms.positions.copy()
self.cell = atoms.get_cell().copy()
energy = 0.0
for i in components.keys():
energy += components[i]
self.energy_free = energy
self.energy_zero = energy
self.results['energy_components'] = components
self.results['energy'] = energy
def calculate_forces(self, atoms):
# calculate the forces based on derivatives of the three EAM functions
self.update(atoms)
self.results['forces'] = np.zeros((len(atoms), 3))
for i in range(len(atoms)): # this is the atom to be embedded
neighbors, offsets = self.neighbors.get_neighbors(i)
offset = np.dot(offsets, atoms.get_cell())
# create a vector of relative positions of neighbors
rvec = atoms.positions[neighbors] + offset - atoms.positions[i]
r = np.sqrt(np.sum(np.square(rvec), axis=1))
nearest = np.arange(len(r))[r < self.cutoff]
d_embedded_energy_i = self.d_embedded_energy[self.index[i]](
self.total_density[i])
urvec = rvec.copy() # unit directional vector
for j in np.arange(len(neighbors)):
urvec[j] = urvec[j] / r[j]
for j_index in range(self.Nelements):
use = self.index[neighbors[nearest]] == j_index
if not use.any():
continue
rnuse = r[nearest][use]
density_j = self.total_density[neighbors[nearest][use]]
if self.form == 'fs':
scale = (self.d_phi[self.index[i], j_index](rnuse) +
(d_embedded_energy_i *
self.d_electron_density[j_index, self.index[i]]
(rnuse)) +
(self.d_embedded_energy[j_index](density_j) *
self.d_electron_density[self.index[i], j_index]
(rnuse)))
else:
scale = (self.d_phi[self.index[i], j_index](rnuse) +
(d_embedded_energy_i *
self.d_electron_density[j_index](rnuse)) +
(self.d_embedded_energy[j_index](density_j) *
self.d_electron_density[self.index[i]](rnuse)))
self.results['forces'][i] += np.dot(scale, urvec[nearest][use])
if (self.form == 'adp'):
adp_forces = self.angular_forces(
self.mu[i], self.mu[neighbors[nearest][use]],
self.lam[i], self.lam[neighbors[nearest][use]], rnuse,
rvec[nearest][use], self.index[i], j_index)
self.results['forces'][i] += adp_forces
def angular_forces(self, mu_i, mu, lam_i, lam, r, rvec, form1, form2):
# calculate the extra components for the adp forces
# rvec are the relative positions to atom i
psi = np.zeros(mu.shape)
for gamma in range(3):
term1 = (mu_i[gamma] - mu[:, gamma]) * self.d[form1][form2](r)
term2 = np.sum(
(mu_i - mu) * self.d_d[form1][form2](r)[:, np.newaxis] *
(rvec * rvec[:, gamma][:, np.newaxis] / r[:, np.newaxis]),
axis=1)
term3 = 2 * np.sum((lam_i[:, gamma] + lam[:, :, gamma]) * rvec *
self.q[form1][form2](r)[:, np.newaxis],
axis=1)
term4 = 0.0
for alpha in range(3):
for beta in range(3):
rs = rvec[:, alpha] * rvec[:, beta] * rvec[:, gamma]
term4 += ((lam_i[alpha, beta] + lam[:, alpha, beta]) *
self.d_q[form1][form2](r) * rs) / r
term5 = ((lam_i.trace() + lam.trace(axis1=1, axis2=2)) *
(self.d_q[form1][form2](r) * r + 2 * self.q[form1][form2]
(r)) * rvec[:, gamma]) / 3.
# the minus for term5 is a correction on the adp
# formulation given in the 2005 Mishin Paper and is posted
# on the NIST website with the AlH potential
psi[:, gamma] = term1 + term2 + term3 + term4 - term5
return np.sum(psi, axis=0)
def adp_dipole(self, r, rvec, d):
# calculate the dipole contribution
mu = np.sum((rvec * d(r)[:, np.newaxis]), axis=0)
return mu # sign to agree with lammps
def adp_quadrupole(self, r, rvec, q):
# slow way of calculating the quadrupole contribution
r = np.sqrt(np.sum(rvec**2, axis=1))
lam = np.zeros([rvec.shape[0], 3, 3])
qr = q(r)
for alpha in range(3):
for beta in range(3):
lam[:, alpha, beta] += qr * rvec[:, alpha] * rvec[:, beta]
return np.sum(lam, axis=0)
def deriv(self, spline):
"""Wrapper for extracting the derivative from a spline"""
def d_spline(aspline):
return spline(aspline, 1)
return d_spline
def plot(self, name=''):
"""Plot the individual curves"""
import matplotlib.pyplot as plt
if self.form == 'eam' or self.form == 'alloy' or self.form == 'fs':
nrow = 2
elif self.form == 'adp':
nrow = 3
else:
raise RuntimeError('Unknown form of potential: %s' % self.form)
if hasattr(self, 'r'):
r = self.r
else:
r = np.linspace(0, self.cutoff, 50)
if hasattr(self, 'rho'):
rho = self.rho
else:
rho = np.linspace(0, 10.0, 50)
plt.subplot(nrow, 2, 1)
self.elem_subplot(rho, self.embedded_energy, r'$\rho$',
r'Embedding Energy $F(\bar\rho)$', name, plt)
plt.subplot(nrow, 2, 2)
if self.form == 'fs':
self.multielem_subplot(r,
self.electron_density,
r'$r$',
r'Electron Density $\rho(r)$',
name,
plt,
half=False)
else:
self.elem_subplot(r, self.electron_density, r'$r$',
r'Electron Density $\rho(r)$', name, plt)
plt.subplot(nrow, 2, 3)
self.multielem_subplot(r, self.phi, r'$r$',
r'Pair Potential $\phi(r)$', name, plt)
plt.ylim(-1.0, 1.0) # need reasonable values
if self.form == 'adp':
plt.subplot(nrow, 2, 5)
self.multielem_subplot(r, self.d, r'$r$', r'Dipole Energy', name,
plt)
plt.subplot(nrow, 2, 6)
self.multielem_subplot(r, self.q, r'$r$', r'Quadrupole Energy',
name, plt)
plt.plot()
def elem_subplot(self, curvex, curvey, xlabel, ylabel, name, plt):
plt.xlabel(xlabel)
plt.ylabel(ylabel)
for i in np.arange(self.Nelements):
label = name + ' ' + self.elements[i]
plt.plot(curvex, curvey[i](curvex), label=label)
plt.legend()
def multielem_subplot(self,
curvex,
curvey,
xlabel,
ylabel,
name,
plt,
half=True):
plt.xlabel(xlabel)
plt.ylabel(ylabel)
for i in np.arange(self.Nelements):
for j in np.arange((i + 1) if half else self.Nelements):
label = name + ' ' + self.elements[i] + '-' + self.elements[j]
plt.plot(curvex, curvey[i, j](curvex), label=label)
plt.legend()
for i in glob('*/'):
if i == '__pycache__/':
continue
dire = i
atoms = read(i + "/" + "POSCAR")
################# These can be added in as arg parsers ##################
ads = read("CO.POSCAR")
surface_atoms = ["Pt"]
radii_multiplier = 1.1
skin_arg = 0.25
no_adsorb = ['']
min_ads_dist = 2.4
nl = NeighborList(natural_cutoffs(atoms, radii_multiplier),
self_interaction=False,
bothways=True,
skin=skin_arg)
nl.update(atoms)
adsorbate_atoms = [
index for index, atom in enumerate(atoms)
if atom.symbol not in surface_atoms
]
normals, mask = generate_normals(atoms,
adsorbate_atoms=adsorbate_atoms,
normalize_final=True)
### make sure to manually set the normals for 2-D materials, all atoms should have a normal pointing up, as all atoms are surface atoms
#normals, mask = np.ones((len(atoms), 3)) * (0, 0, 1), list(range(len(atoms)))
constrained = constrained_indices(atoms)
class SHPP(Calculator):
""" Soft+Harmonic Pair Potential -- a combination
of LAMMPS-pair_style 'soft' pair potential
plus restorative forces.
The total energy is given by:
E_tot(R) = E_harm(R) + E_soft(R)
E_harm(R) = Sum_i 0.5*k*|R_i-R_i,start|^2
E_soft(R) = Sum_i<j A*(1+cos(|R_i-R_j|*pi/d_min))
atoms: an Atoms object
blmin: dictionary with the minimal interatomic distance
for each (sorted) pair of atomic numbers
k: spring constant for the harmonic potential in eV/Angstrom^2
A: prefactor for the 'soft' potential in eV
"""
implemented_properties = ['energy', 'forces']
def __init__(self, atoms, blmin, k=0.5, A=10.):
Calculator.__init__(self)
self.positions = atoms.get_positions()
self.blmin = blmin
self.k = k
self.A = A
self.N = len(atoms)
rcut = max(self.blmin.values())
self.nl = NeighborList([rcut / 2.] * self.N,
skin=1.,
bothways=True,
self_interaction=False)
def calculate(self, atoms, properties, system_changes):
Calculator.calculate(self, atoms, properties, system_changes)
energy, forces = 0, np.zeros((self.N, 3))
e, f = self._calculate_harm(atoms)
energy += e
forces += f
e, f = self._calculate_soft(atoms)
energy += e
forces += f
self.results = {'energy': energy, 'forces': forces}
def _calculate_harm(self, atoms):
cell = atoms.get_cell()
pbc = atoms.get_pbc()
vectors = atoms.get_positions() - self.positions
e = 0.
f = np.zeros((self.N, 3))
for i, v in enumerate(vectors):
v, d = find_mic([v], cell, pbc)
e += 0.5 * self.k * (d**2)
f[i] = -self.k * v
return e, f
def _calculate_soft(self, atoms):
cell = atoms.get_cell()
num = atoms.get_atomic_numbers()
pos = atoms.get_positions()
self.nl.update(atoms)
e = 0
f = np.zeros((self.N, 3))
for i in range(self.N):
indices, offsets = self.nl.get_neighbors(i)
p = pos[indices] + np.dot(offsets, cell)
r = cdist(p, [pos[i]])
v = p - pos[i]
for j, index in enumerate(indices):
bl = self.blmin[tuple(sorted([num[i], num[index]]))]
d = r[j][0]
if d < bl:
e += self.A * (1 + np.cos(d * np.pi / bl))
fj = self.A * np.pi * np.sin(np.pi * d / bl)
fj /= (d * bl) * v[j]
f[index] += fj
return e, f
def load_oqmd_data(num_dist_basis, dtype=float, cutoff=2.0, filter_query=None):
""" Returns tuple (Z, D, y, num_species)
where
Z is a matrix, each row in Z corresponds to a molecule and the elements
are atomic numbers
D is a 4D tensor giving the Gaussian feature expansion of distances
between atoms
y is the energy of each molecule in kcal/mol
num_species is the integer number of different atomic species in Z """
import ase.db
con = ase.db.connect("oqmd_all_entries.db")
sel = filter_query
# Create sorted list of species
all_species = sorted(
list(
reduce(lambda x, y: x.union(set(y.numbers)), con.select(sel),
set())))
# Insert dummy species 0
all_species.insert(0, 0)
# Create mapping from species to species index
species_map = dict([(x, i) for i, x in enumerate(all_species)])
# Find max number of atoms
max_atoms = 0
num_molecules = 0
for row in con.select(sel):
num_molecules += 1
atoms = row.toatoms()
max_atoms = max(max_atoms, len(atoms))
# Gaussian basis function parameters
mu_min = -1
mu_max = 2 * cutoff + 1
step = (mu_max - mu_min) / num_dist_basis
sigma = step
print "Number of molecules %d, max atoms %d" % (num_molecules, max_atoms)
k = np.arange(num_dist_basis)
D = np.zeros((num_molecules, max_atoms, max_atoms, num_dist_basis),
dtype=dtype)
Z = np.zeros((num_molecules, max_atoms), dtype=np.int8)
y = np.zeros(num_molecules, dtype=dtype)
for i_mol, row in enumerate(con.select(sel)):
print "feature expansion %10d/%10d\r" % (i_mol + 1, num_molecules),
atoms = row.toatoms()
y[i_mol] = row.total_energy
Z[i_mol, 0:len(row.numbers)] = map(lambda x: species_map[x],
row.numbers)
assert np.all(atoms.get_atomic_numbers() == row.numbers)
neighborhood = NeighborList([cutoff] * len(atoms),
self_interaction=False,
bothways=False)
neighborhood.build(atoms)
for ii in range(len(atoms)):
neighbor_indices, offset = neighborhood.get_neighbors(ii)
for jj, offs in zip(neighbor_indices, offset):
ii_pos = atoms.positions[ii]
jj_pos = atoms.positions[jj] + np.dot(offs, atoms.get_cell())
dist = np.linalg.norm(ii_pos - jj_pos)
d_expand = np.exp(-((dist - (mu_min + k * step))**2.0) /
(2.0 * sigma**2.0))
D[i_mol, ii, jj, :] += d_expand
if jj != ii:
D[i_mol, jj, ii, :] += d_expand
return Z, D, y, len(all_species)
def generate_site_type(atoms, surface_mask, normals, coordination, unallowed_elements=[]):
cutoffs = natural_cutoffs(atoms)
nl = NeighborList(cutoffs, self_interaction=False, bothways=True)
nl.update(atoms)
surface_mask = [index for index in surface_mask if atoms[index].symbol not in unallowed_elements]
possible = list(combinations(set(surface_mask), coordination))
valid = []
sites = []
for cycle in possible:
for start, end in combinations(cycle, 2):
if end not in nl.get_neighbors(start)[0]:
break
else: # All were valid
valid.append(list(cycle))
#print(valid)
for cycle in valid:
tracked = np.array(atoms[cycle[0]].position, dtype=float)
known = np.zeros(shape=(coordination, 3), dtype=float)
known[0] = tracked
for index, (start, end) in enumerate(zip(cycle[:-1], cycle[1:])):
for neighbor, offset in zip(*nl.get_neighbors(start)):
if neighbor == end:
tracked += offset_position(atoms, neighbor, offset) - atoms[start].position
known[index + 1] = tracked
average = np.average(known, axis=0)
normal = np.zeros(3)
#for index in cycle:
#neighbors = len(nl.get_neighbors(index)[0])
#normal += normals[index] * (1/neighbors)
#normal = normalize(normal)
#for index in cycle:
#print(cycle)
if len(cycle) == 1:
for index in cycle:
neighbors = len(nl.get_neighbors(index)[0])
normal += normals[index] * (1/neighbors)
normal = normalize(normal)
if len(cycle) >1:
neighbors = len(nl.get_neighbors(index)[0])
cycle_orig = cycle
#print(cycle)
normal = generate_normals_new(atoms,cycle_orig,nl,surface_mask)
#print(cycle,normal)
for index in cycle:
neighbors = len(nl.get_neighbors(index)[0])
normal += normals[index] * (1/neighbors)
normal = normalize(normal)
if coordination ==2:
average[2] = average[2] - 0.5
if coordination == 3:
average[2] = average[2] -0.7
#print(average)
#print(average[2])
site_ads =Site(cycle=cycle, position=average, normal=normal)
sites.append(site_ads)
return sites
def CoreShellCN(atoms, type_a, type_b, ratio, R_min = 1.5, CN_max=12, n_depth=-1):
r"""This routine generates cluster with ideal core-shell architecture,
so that atoms of type_a are placed on the surface
and atoms of type_b are forming the core of nanoparticle.
The 'surface' of nanoparticle is defined as atoms
with unfinished first coordination shell.
Used algorithm without need for explicit knowledge of
far coordination shells parameters, as it was required in CoreShellFCC(..)
Parameters
----------
atoms: ase.Atoms
ase Atoms object, containing atomic cluster.
type_a: string
Symbol of chemical element to be placed on the shell.
type_b: string
Symbol of chemical element to be placed in the core.
ratio: float
Guards the number of shell atoms, type_a:type_b = ratio:(1-ratio)
R_min: float
Typical bond length. Neighboring atoms within this value are counted
as coordination numbers.
Default is 3.0.
CN_max: float
Maximum possible coordination number (bulk coordination number).
Default is 12.
n_depth: int
Number of layers of the shell formed by atoms ratio.
Default value -1 is ignored and n_depth is calculated according
ratio. If n_depth is set then value of ratio is ignored.
Returns
-------
Function returns ASE atoms object which
contains bimetallic core-shell cluster
Example
--------
>>> atoms = FaceCenteredCubic('Ag',
[(1, 0, 0), (1, 1, 0), (1, 1, 1)], [7,8,7], 4.09)
>>> atoms = CoreShellCN(atoms, 'Pt', 'Ag', 0.5)
>>> view(atoms)
"""
# 0 < ratio < 1
target_x = ratio
if n_depth != -1:
target_x = 1
n_atoms = len(atoms)
n_a = (np.array(atoms.get_chemical_symbols()) == type_a).sum()
#n_b = (atoms.get_chemical_symbols() == type_b).sum()
#print n_a
n_shell = 0 # depth of the shell
while (n_a < n_atoms * target_x):
n_shell += 1
print ("shell: ", n_shell)
if (n_depth != -1)and(n_shell > n_depth):
break
neiblist = NeighborList( [ R_min ] * n_atoms,
self_interaction=False, bothways=True )
neiblist.build( atoms )
for i in xrange( n_atoms ):
indeces, offsets = neiblist.get_neighbors(i)
if (atoms[i].symbol == type_b):
CN_temp = 0
for ii in indeces:
if atoms[ii].symbol == type_b:
CN_temp += 1
#print "CN_temp: ", CN_temp
if (CN_temp < CN_max):
# coord shell is not full, swap type to type_a!
atoms[i].tag = n_shell # not swap yet, but mark
# swap atom types now. Stop if target ratio achieved
for atom in atoms:
if (atom.tag > 0)&(atom.symbol == type_b):
if n_a < n_atoms * target_x:
atom.symbol = type_a
n_a += 1
#print "n_A: ", n_a
# end while
# check number of atoms
checkn_a = 0
for element in atoms.get_chemical_symbols():
if element == type_a:
checkn_a += 1
#print "Should be equal: ", n_a, checkn_a
assert n_a == checkn_a
return atoms
def test_nl(atoms, cutoff):
cutoffs = [cutoff/2]*len(atoms)
nl = NeighborList(cutoffs, skin=0, bothways=True, self_interaction=False)
nl.update(atoms)
for i in range(len(atoms)):
(x, _) = nl.get_neighbors(i)
class EMT(Calculator):
"""Python implementation of the Effective Medium Potential.
Supports the following standard EMT metals:
Al, Cu, Ag, Au, Ni, Pd and Pt.
In addition, the following elements are supported.
They are NOT well described by EMT, and the parameters
are not for any serious use:
H, C, N, O
The potential takes a single argument, ``asap_cutoff``
(default: False). If set to True, the cutoff mimics
how Asap does it; most importantly the global cutoff
is chosen from the largest atom present in the simulation,
if False it is chosen from the largest atom in the parameter
table. True gives the behaviour of the Asap code and
older EMT implementations, although the results are not
bitwise identical.
"""
implemented_properties = [
'energy', 'forces', 'stress', 'magmom', 'magmoms'
]
nolabel = True
default_parameters = {'asap_cutoff': False}
def __init__(self, **kwargs):
Calculator.__init__(self, **kwargs)
def initialize(self, atoms):
self.par = {}
self.rc = 0.0
self.numbers = atoms.get_atomic_numbers()
if self.parameters.asap_cutoff:
relevant_pars = {}
for symb, p in parameters.items():
if atomic_numbers[symb] in self.numbers:
relevant_pars[symb] = p
else:
relevant_pars = parameters
maxseq = max(par[1] for par in relevant_pars.values()) * Bohr
rc = self.rc = beta * maxseq * 0.5 * (sqrt(3) + sqrt(4))
rr = rc * 2 * sqrt(4) / (sqrt(3) + sqrt(4))
self.acut = np.log(9999.0) / (rr - rc)
if self.parameters.asap_cutoff:
self.rc_list = self.rc * 1.045
else:
self.rc_list = self.rc + 0.5
for Z in self.numbers:
if Z not in self.par:
sym = chemical_symbols[Z]
if sym not in parameters:
raise NotImplementedError(
'No EMT-potential for {0}'.format(sym))
p = parameters[sym]
s0 = p[1] * Bohr
eta2 = p[3] / Bohr
kappa = p[4] / Bohr
x = eta2 * beta * s0
gamma1 = 0.0
gamma2 = 0.0
for i, n in enumerate([12, 6, 24]):
r = s0 * beta * sqrt(i + 1)
x = n / (12 * (1.0 + exp(self.acut * (r - rc))))
gamma1 += x * exp(-eta2 * (r - beta * s0))
gamma2 += x * exp(-kappa / beta * (r - beta * s0))
self.par[Z] = {
'E0': p[0],
's0': s0,
'V0': p[2],
'eta2': eta2,
'kappa': kappa,
'lambda': p[5] / Bohr,
'n0': p[6] / Bohr**3,
'rc': rc,
'gamma1': gamma1,
'gamma2': gamma2
}
self.ksi = {}
for s1, p1 in self.par.items():
self.ksi[s1] = {}
for s2, p2 in self.par.items():
self.ksi[s1][s2] = p2['n0'] / p1['n0']
self.forces = np.empty((len(atoms), 3))
self.stress = np.empty((3, 3))
self.sigma1 = np.empty(len(atoms))
self.deds = np.empty(len(atoms))
self.nl = NeighborList([0.5 * self.rc_list] * len(atoms),
self_interaction=False)
def calculate(self,
atoms=None,
properties=['energy'],
system_changes=all_changes):
Calculator.calculate(self, atoms, properties, system_changes)
if 'numbers' in system_changes:
self.initialize(self.atoms)
positions = self.atoms.positions
numbers = self.atoms.numbers
cell = self.atoms.cell
self.nl.update(self.atoms)
self.energy = 0.0
self.sigma1[:] = 0.0
self.forces[:] = 0.0
self.stress[:] = 0.0
natoms = len(self.atoms)
for a1 in range(natoms):
Z1 = numbers[a1]
p1 = self.par[Z1]
ksi = self.ksi[Z1]
neighbors, offsets = self.nl.get_neighbors(a1)
offsets = np.dot(offsets, cell)
for a2, offset in zip(neighbors, offsets):
d = positions[a2] + offset - positions[a1]
r = sqrt(np.dot(d, d))
if r < self.rc_list:
Z2 = numbers[a2]
p2 = self.par[Z2]
self.interact1(a1, a2, d, r, p1, p2, ksi[Z2])
for a in range(natoms):
Z = numbers[a]
p = self.par[Z]
try:
ds = -log(self.sigma1[a] / 12) / (beta * p['eta2'])
except (OverflowError, ValueError):
self.deds[a] = 0.0
self.energy -= p['E0']
continue
x = p['lambda'] * ds
y = exp(-x)
z = 6 * p['V0'] * exp(-p['kappa'] * ds)
self.deds[a] = ((x * y * p['E0'] * p['lambda'] + p['kappa'] * z) /
(self.sigma1[a] * beta * p['eta2']))
self.energy += p['E0'] * ((1 + x) * y - 1) + z
for a1 in range(natoms):
Z1 = numbers[a1]
p1 = self.par[Z1]
ksi = self.ksi[Z1]
neighbors, offsets = self.nl.get_neighbors(a1)
offsets = np.dot(offsets, cell)
for a2, offset in zip(neighbors, offsets):
d = positions[a2] + offset - positions[a1]
r = sqrt(np.dot(d, d))
if r < self.rc_list:
Z2 = numbers[a2]
p2 = self.par[Z2]
self.interact2(a1, a2, d, r, p1, p2, ksi[Z2])
self.results['energy'] = self.energy
self.results['free_energy'] = self.energy
self.results['forces'] = self.forces
if 'stress' in properties:
if self.atoms.number_of_lattice_vectors == 3:
self.stress += self.stress.T.copy()
self.stress *= -0.5 / self.atoms.get_volume()
self.results['stress'] = self.stress.flat[[0, 4, 8, 5, 2, 1]]
else:
raise PropertyNotImplementedError
def interact1(self, a1, a2, d, r, p1, p2, ksi):
x = exp(self.acut * (r - self.rc))
theta = 1.0 / (1.0 + x)
y1 = (0.5 * p1['V0'] * exp(-p2['kappa'] * (r / beta - p2['s0'])) *
ksi / p1['gamma2'] * theta)
y2 = (0.5 * p2['V0'] * exp(-p1['kappa'] * (r / beta - p1['s0'])) /
ksi / p2['gamma2'] * theta)
self.energy -= y1 + y2
f = ((y1 * p2['kappa'] + y2 * p1['kappa']) / beta +
(y1 + y2) * self.acut * theta * x) * d / r
self.forces[a1] += f
self.forces[a2] -= f
self.stress -= np.outer(f, d)
self.sigma1[a1] += (exp(-p2['eta2'] * (r - beta * p2['s0'])) * ksi *
theta / p1['gamma1'])
self.sigma1[a2] += (exp(-p1['eta2'] * (r - beta * p1['s0'])) / ksi *
theta / p2['gamma1'])
def interact2(self, a1, a2, d, r, p1, p2, ksi):
x = exp(self.acut * (r - self.rc))
theta = 1.0 / (1.0 + x)
y1 = (exp(-p2['eta2'] * (r - beta * p2['s0'])) * ksi / p1['gamma1'] *
theta * self.deds[a1])
y2 = (exp(-p1['eta2'] * (r - beta * p1['s0'])) / ksi / p2['gamma1'] *
theta * self.deds[a2])
f = ((y1 * p2['eta2'] + y2 * p1['eta2']) +
(y1 + y2) * self.acut * theta * x) * d / r
self.forces[a1] -= f
self.forces[a2] += f
self.stress += np.outer(f, d)
d = 0.0
for a in range(len(atoms)):
i, offsets = nl.get_neighbors(a)
for j in i:
c[j] += 1
c[a] += len(i)
d += (((R[i] + np.dot(offsets, cell) - R[a])**2).sum(1)**0.5).sum()
return d, c
for sorted in [False, True]:
for p1 in range(2):
for p2 in range(2):
for p3 in range(2):
# print(p1, p2, p3)
atoms.set_pbc((p1, p2, p3))
nl = NeighborList(atoms.numbers * 0.2 + 0.5,
skin=0.0, sorted=sorted)
nl.update(atoms)
d, c = count(nl, atoms)
atoms2 = atoms.repeat((p1 + 1, p2 + 1, p3 + 1))
nl2 = NeighborList(atoms2.numbers * 0.2 + 0.5,
skin=0.0, sorted=sorted)
nl2.update(atoms2)
d2, c2 = count(nl2, atoms2)
c2.shape = (-1, 10)
dd = d * (p1 + 1) * (p2 + 1) * (p3 + 1) - d2
# print(dd)
# print(c2 - c)
assert abs(dd) < 1e-10
assert not (c2 - c).any()
h2 = Atoms('H2', positions=[(0, 0, 0), (0, 0, 1)])
def calculate(
self,
atoms=None,
properties=None,
system_changes=all_changes,
):
if properties is None:
properties = self.implemented_properties
Calculator.calculate(self, atoms, properties, system_changes)
natoms = len(self.atoms)
sigma = self.parameters.sigma
epsilon = self.parameters.epsilon
rc = self.parameters.rc
if self.nl is None or 'numbers' in system_changes:
self.nl = NeighborList([rc / 2] * natoms, self_interaction=False)
self.nl.update(self.atoms)
positions = self.atoms.positions
cell = self.atoms.cell
# potential value at rc
e0 = 4 * epsilon * ((sigma / rc)**12 - (sigma / rc)**6)
atomic_energies = np.zeros(natoms)
forces = np.zeros((natoms, 3))
stresses = np.zeros((natoms, 3, 3))
for ii in range(natoms):
neighbors, offsets = self.nl.get_neighbors(ii)
cells = np.dot(offsets, cell)
# pointing *towards* neighbours
distance_vectors = positions[neighbors] + cells - positions[ii]
r2 = (distance_vectors**2).sum(1)
c6 = (sigma**2 / r2)**3
c6[r2 > rc**2] = 0.0
c12 = c6**2
pairwise_energies = 4 * epsilon * (c12 - c6) - e0 * (c6 != 0.0)
atomic_energies[ii] += 0.5 * pairwise_energies.sum(
) # atomic energies
pairwise_forces = (-24 * epsilon * (2 * c12 - c6) /
r2)[:, np.newaxis] * distance_vectors
forces[ii] += pairwise_forces.sum(axis=0)
stresses[ii] += 0.5 * np.dot(
pairwise_forces.T,
distance_vectors) # equivalent to outer product
# add j < i contributions
for jj, atom_j in enumerate(neighbors):
atomic_energies[atom_j] += 0.5 * pairwise_energies[jj]
forces[atom_j] += -pairwise_forces[jj] # f_ji = - f_ij
stresses[atom_j] += 0.5 * np.outer(pairwise_forces[jj],
distance_vectors[jj])
# no lattice, no stress
if self.atoms.number_of_lattice_vectors == 3:
stresses = full_3x3_to_voigt_6_stress(stresses)
self.results['stress'] = (stresses.sum(axis=0) /
self.atoms.get_volume())
self.results['stresses'] = stresses / self.atoms.get_volume()
energy = atomic_energies.sum()
self.results['energy'] = energy
self.results['atomic_energies'] = atomic_energies
self.results['free_energy'] = energy
self.results['forces'] = forces
def calculate(self, crystal, ids=None):
"""Calculate and return the EAD.
Parameters
----------
crystal: object
ASE Structure object.
ids: list
A list of the centered atoms to be computed
if None, all atoms will be considered
Returns
-------
d: dict
The user-defined EAD that represent the crystal.
d = {'x': [N, d], 'dxdr': [N, layer, d, 3], 'rdxdr': [N, layer, d, 3, 3],
'elements': list of elements}
"""
self.crystal = crystal
self.total_atoms = len(crystal) # total atoms in the unit cell
vol = crystal.get_volume()
rc = [self.Rc / 2.] * self.total_atoms
neighbors = NeighborList(rc, self_interaction=False, bothways=True, skin=0.)
neighbors.update(crystal)
unique_N = 0
for i in range(self.total_atoms):
indices, offsets = neighbors.get_neighbors(i)
ith = 0
if i not in indices:
ith += 1
unique_N += len(np.unique(indices)) + ith # +1 is for i
# Make numpy array here
self.d = {'x': np.zeros([self.total_atoms, self.dsize]), 'elements': []}
if self.derivative:
self.d['dxdr'] = np.zeros([unique_N, self.dsize, 3])
self.d['seq'] = np.zeros([unique_N, 2], dtype=int)
if self.stress:
self.d['rdxdr'] = np.zeros([unique_N, self.dsize, 3, 3])
seq_count = 0
if ids is None:
ids = range(len(crystal))
for i in ids: # range(self.total_atoms):
element = crystal.get_chemical_symbols()[i]
indices, offsets = neighbors.get_neighbors(i)
Z = [] # atomic numbers of neighbors
assert len(indices) > 0, \
f"There's no neighbor for this structure at Rc = {self.Rc} A."
Ri = crystal.get_positions()[i]
total_neighbors = len(indices)
Rj = np.zeros([total_neighbors, 3])
IDs = np.zeros(total_neighbors, dtype=int)
count = 0
for j, offset in zip(indices, offsets):
Rj[count, :] = crystal.positions[j] + np.dot(offset, crystal.get_cell())
IDs[count] = j
Z.append(crystal[j].number)
count += 1
Z = np.array(Z)
Rij = Rj - Ri
Dij = np.sqrt(np.sum(Rij ** 2, axis=1))
d = calculate_eamd(i, self.total_atoms, Rij, Dij, Z, IDs, self.Rc,
self.parameters, self.derivative, self.stress)
self.d['x'][i] = d['x']
if self.derivative:
n_seq = len(d['seq'])
self.d['dxdr'][seq_count:seq_count + n_seq] = d['dxdr']
self.d['seq'][seq_count:seq_count + n_seq] = d['seq']
if self.stress:
self.d['rdxdr'][seq_count:seq_count + n_seq] = -d['rdxdr'] / vol
if self.derivative:
seq_count += n_seq
self.d['elements'].append(element)
return self.d
def get_neighbours(atoms, r_cut, self_interaction=False):
"""Return a list of pairs of atoms within a given distance of each other.
If matscipy can be imported, then this will directly call matscipy's
neighbourlist function. Otherwise it will use ASE's NeighborList object.
Args:
atoms: ase.atoms object to calculate neighbours for
r_cut: cutoff radius (float). Pairs of atoms are considered neighbours
if they are within a distance r_cut of each other (note that this
is double the parameter used in the ASE's neighborlist module)
Returns: a tuple (i_list, j_list, d_list, fixed_atoms):
i_list, j_list: i and j indices of each neighbour pair
d_list: absolute distance between the corresponding pair
fixed_atoms: indices of any fixed atoms
"""
if isinstance(atoms, Filter):
atoms = atoms.atoms
if have_matscipy:
i_list, j_list, d_list = neighbour_list('ijd', atoms, r_cut)
else:
radii = [r_cut / 2 for i in range(len(atoms))]
nl = NeighborList(radii,
sorted=False,
self_interaction=False,
bothways=True)
nl.update(atoms)
i_list = []
j_list = []
d_list = []
for i, atom in enumerate(atoms):
posn_i = atom.position
indices, offsets = nl.get_neighbors(i)
assert len(indices) == len(offsets)
for j, offset in zip(indices, offsets):
# Offsets represent how far away an atom is from its pair in terms
# of the repeating cell - for instance, an atom i might be in cell
# (0, 0, 0) while the neighbouring atom j is in cell (0, 1, 1). To
# get the true position we have to correct for the offset:
posn_j = atoms.positions[j] + np.dot(offset, atoms.get_cell())
distance = np.sqrt(((posn_j - posn_i)**2).sum())
i_list.append(i)
j_list.append(j)
d_list.append(distance)
i_list = np.array(i_list)
j_list = np.array(j_list)
d_list = np.array(d_list)
# filter out self-interactions (across PBC)
if not self_interaction:
mask = i_list != j_list
i_list = i_list[mask]
j_list = j_list[mask]
d_list = d_list[mask]
# filter out bonds where 1st atom (i) in pair is fixed
fixed_atoms = []
for constraint in atoms.constraints:
if isinstance(constraint, FixAtoms):
fixed_atoms.extend(list(constraint.index))
return i_list, j_list, d_list, fixed_atoms
def biatomic(self, A, B, R1=3.0, calc_energy=False):
r"""This routine analyzes atomic structure
by the calculation of coordination numbers
in cluster with atoms of two types (A and B).
Parameters
----------
A: string
atom type, like 'Ag', 'Pt', etc.
B: string
atom type, like 'Ag', 'Pt', etc.
R1: float
First coordination shell will icnlude all atoms
with distance less then R1 [Angstrom].
Default value is 3.
calc_energy: bool
Flag used for calculation of potential energy with EMT
calculator. The default value is False, so that
energy is not calculated.
Returns
-------
N: int
number of atoms in cluster
nA:
number of atoms of type A
R: float
radius of the cluster
CN_AA: float
average number of atoms A around atom A
CN_AB: float
average number of atoms A around atom B
CN_BB: float
average number of atoms B around atom B
CN_BA: float
average number of atoms B around atom A
etha: float
parameter of local ordering, -1 < etha < 1.
Returns 999 if concentration of one of the
component is too low.
E: float
potential energy
NAcore:
number of A atoms in core
NBcore:
number of B atoms in core
CNshellAA:
average CN of A-A for surface atoms only
CNshellAB:
average CN of A-B for surface atoms only
CNshellBB:
average CN of B-B for surface atoms only
CNshellBA:
average CN of B-A for surface atoms only
Notes
-----
The radius of the cluster is roughly determined as
maximum the distance from the center to most distant atom
in the cluster.
Example
--------
>>> atoms = FaceCenteredCubic('Ag',
[(1, 0, 0), (1, 1, 0), (1, 1, 1)], [7,8,7], 4.09)
>>> atoms = CoreShellFCC(atoms, 'Pt', 'Ag', 0.6, 4.09)
>>> [N, nA, R, CN_AA, CN_AB, CN_BB, CN_BA, etha] =
biatomic(atoms, 'Pt', 'Ag')
>>> print "Short range order parameter: ", etha
"""
self.chems = [A, B] # for now used for report only
N = len(self.atoms)
nA = 0
nB = 0
for element in self.atoms.get_chemical_symbols():
if element == A:
nA += 1
elif element == B:
nB += 1
else:
raise Exception('Extra element ' + element)
if (nA + nB != N):
raise Exception('Number of A (' + str(nA) + ') ' +
'and B (' + str(nB) + ') artoms mismatch!')
nl = NeighborList([0.5 * R1] * N, self_interaction=False, bothways=True)
nl.build(self.atoms)
# initialize counters:
CN_AA = 0 # averaged total coord. numbers
CN_AB = 0
CN_BB = 0
CN_BA = 0
NAcore = 0 # number of atoms in core region
NBcore = 0
CNshellAA = 0 # average coord. numbers for surface atoms
CNshellAB = 0
CNshellBB = 0
CNshellBA = 0
for iatom in xrange(0, N):
#print "central atom index:", iatom, " kind: ", self.atoms[iatom].symbol
indeces, offsets = nl.get_neighbors(iatom)
if self.atoms[iatom].symbol == B:
CN_BB_temp = 0
CN_BA_temp = 0
for ii in indeces:
#print "neighbor atom index:", ii, " kind: ", self.atoms[ii].symbol
if self.atoms[ii].symbol == B:
CN_BB_temp += 1
elif self.atoms[ii].symbol == A:
CN_BA_temp += 1
else:
print("Warning: unknown atom type %s. It will not be counted!"%self.atoms[ii].symbol)
CN_BB += CN_BB_temp
CN_BA += CN_BA_temp
if len(indeces) < 12:
# SHELL
CNshellBB += CN_BB_temp
CNshellBA += CN_BA_temp
else:
# CORE
NBcore += 1
elif self.atoms[iatom].symbol == A:
CN_AA_temp = 0
CN_AB_temp = 0
for i in indeces:
#print "neighbor atom index:", i, " kind: ", self.atoms[i].symbol
if self.atoms[i].symbol == A:
CN_AA_temp += 1
elif self.atoms[i].symbol == B:
CN_AB_temp += 1
else:
print("Warning: unknown atom type %s. It will not be counted!"%self.atoms[i].symbol)
CN_AA += CN_AA_temp
CN_AB += CN_AB_temp
if len(indeces) < 12:
# SHELL
CNshellAA += CN_AA_temp
CNshellAB += CN_AB_temp
else:
# CORE
NAcore += 1
else:
#raise Exception("Un")
print("Warning: unknown atom type %s. It will not be counted!"%self.atoms[iatom].symbol)
# averaging:
CN_AA = CN_AA * 1.0 / nA
CN_AB = CN_AB * 1.0 / nA
CN_BB = CN_BB * 1.0 / nB
CN_BA = CN_BA * 1.0 / nB
znam = (nA - NAcore)
if znam > 0.0001:
CNshellAA = CNshellAA * 1.0 / znam
CNshellAB = CNshellAB * 1.0 / znam
else:
CNshellAA = 0
CNshellAB = 0
znam = (nB - NBcore)
if znam > 0.0001:
CNshellBB = CNshellBB * 1.0 / znam
CNshellBA = CNshellBA * 1.0 / znam
else:
CNshellBB = 0
CNshellBA = 0
# calc concentrations:
concB = nB * 1.0 / N
znam = concB * (CN_AA + CN_AB)
if znam < 0.0001:
#print "WARNING! Too low B concentration: ",concB
etha = 999
else:
etha = 1 - CN_AB / znam
R = self.atoms.positions.max() / 2.0
if calc_energy:
#from asap3 import EMT
from ase.calculators.emt import EMT
self.atoms.set_calculator(EMT())
E = self.atoms.get_potential_energy()
else:
E = -1
#return N, nA, R, CN_AA, CN_AB, CN_BB, CN_BA, etha, E, NAcore, \
# NBcore, CNshellAA, CNshellAB, CNshellBB, CNshellBA
self.N = N
self.nA = nA
self.R = R
self.CN_AA = CN_AA #TODO: use only arrays of CNs
self.CN_AB = CN_AB
self.CN_BB = CN_BB
self.CN_BA = CN_BA
self.CNs = np.array([ [CN_AA, CN_AB], [CN_BA, CN_BB] ])
self.etha = etha
self.E = E
self.NAcore = NAcore
self.NBcore = NBcore
self.CNshellAA = CNshellAA
self.CNshellAB = CNshellAB
self.CNshellBB = CNshellBB
self.CNshellBA = CNshellBA
def find_layers( # pylint: disable=too-many-locals,too-many-statements,too-many-branches
asecell,
factor=1.1):
"""
Obtains all subunits of a given structure by looking
at the connectivity of the bonds.
:param asecell: the bulk unit cell (in ase.Atoms format)
:param factor: the skin factor
:return: a tuple with a boolean indicating if the material is layered, a list of layers in the structure (ase format),
a list of indices of the atoms in each layer, and a rotated bulk ASE cell (with stacking axis along z).
MOREOVER, it 1) returns layers ordered by stacking index and 2) makes sure the layer is connected when
removing the PBC along the third (stacking) axis.
"""
tol = 1.0e-6
nl = NeighborList(
factor * get_covalent_radii_array(asecell),
bothways=True,
self_interaction=False,
skin=0.0,
)
nl.update(asecell)
vector1, vector2, vector3 = asecell.cell
is_layered = True
layer_structures = []
layer_indices = []
visited = []
aselayer = None
final_layered_structures = None
# Loop over atoms (idx: atom index)
for idx in range(len(asecell)): # pylint: disable=too-many-nested-blocks
# Will contain the indices of the atoms in the "current" layer
layer = []
# Check if I already visited this atom
if idx not in visited:
# Update 'layer' and 'visited'
check_neighbors(idx, nl, asecell, visited, layer)
aselayer = asecell.copy()[layer]
layer_nl = NeighborList(
factor * get_covalent_radii_array(aselayer),
bothways=True,
self_interaction=False,
skin=0.0,
)
layer_nl.update(aselayer)
# We search for the periodic images of the first atom (idx=0)
# that are connected to at least one atom of the connected layer
neigh_vec = []
for idx2 in range(len(aselayer)):
_, offsets = layer_nl.get_neighbors(idx2)
for offset in offsets:
if not all(offset == [0, 0, 0]):
neigh_vec.append(offset)
# We define the dimensionality as the rank
dim = np.linalg.matrix_rank(neigh_vec)
if dim == 2:
cell = asecell.cell
vectors = list(np.dot(neigh_vec, cell))
iv = shortest_vector_index(vectors)
vector1 = vectors.pop(iv)
iv = shortest_vector_index(vectors)
vector2 = vectors.pop(iv)
vector3 = np.cross(vector1, vector2)
while np.linalg.norm(vector3) < tol:
iv = shortest_vector_index(vectors)
vector2 = vectors.pop(iv)
vector3 = np.cross(vector1, vector2)
vector1, vector2 = gauss_reduce(vector1, vector2)
vector3 = np.cross(vector1, vector2)
aselayer = _update_and_rotate_cell(
aselayer, [vector1, vector2, vector3],
[list(range(len(aselayer)))])
disconnected = []
for i in range(-3, 4):
for j in range(-3, 4):
for k in range(-3, 4):
vector = i * cell[0] + j * cell[1] + k * cell[2]
if np.dot(vector3, vector) > tol:
disconnected.append(vector)
iv = shortest_vector_index(disconnected)
vector3 = disconnected[iv]
layer_structures.append(aselayer)
layer_indices.append(layer)
else:
is_layered = False
if is_layered:
newcell = [vector1, vector2, vector3]
if abs(np.linalg.det(newcell) / np.linalg.det(cell) - 1.0) > 1e-3:
raise ValueError(
"An error occurred. The new cell after rotation has a different volume than the original cell"
)
rotated_asecell = _update_and_rotate_cell(asecell, newcell,
layer_indices)
# Re-order layers according to their projection
# on the stacking direction
vert_direction = np.cross(rotated_asecell.cell[0],
rotated_asecell.cell[1])
vert_direction /= np.linalg.norm(vert_direction)
stack_proj = [
np.dot(layer.positions, vert_direction).mean()
for layer in [rotated_asecell[il] for il in layer_indices]
]
stack_order = np.argsort(stack_proj)
# order layers with increasing coordinate along the stacking direction
layer_indices = [layer_indices[il] for il in stack_order]
# Move the atoms along the third lattice vector so that
# the first layer has zero projection along the vertical direction
trans_vector = -(stack_proj[stack_order[0]] / np.dot(
vert_direction, rotated_asecell.cell[2]) * rotated_asecell.cell[2])
rotated_asecell.translate(trans_vector)
# I don't return the 'layer_structures' because there the atoms are moved
# from their positions and the z axis lenght might not be appropriate
final_layered_structures = [
rotated_asecell[this_layer_indices]
for this_layer_indices in layer_indices
]
else:
rotated_asecell = None
if not is_layered:
aselayer = None
return is_layered, final_layered_structures, layer_indices, rotated_asecell
def monoatomic(self, R1=3, calc_energy=False):
r"""This routine analyzes atomic structure
by the calculation of coordination numbers
in cluster with only one type of atom.
Parameters
----------
R1: float
First coordination shell will icnlude all atoms
with distance less then R1 [Angstrom].
Default value is 3.
calc_energy: bool
Flag used for calculation of potential energy with EMT
calculator. The default value is False, so that
energy is not calculated.
Returns
-------
N: int
number of atoms in cluster
R: float
radius of the cluster
CN: float
average coord number
E: float
potential energy, -1 if calc_energy is False
Ncore:
number of atoms in core region (number of atoms with
all 12 neighbors)
CNshell:
average coordination number for surface atoms only
Notes
-----
The radius of the cluster is roughly determined as
maximum the distance from the center to most distant atom
in the cluster.
Example
--------
>>> atoms = FaceCenteredCubic('Ag',
[(1, 0, 0), (1, 1, 0), (1, 1, 1)], [7,8,7], 4.09)
>>> qsar = QSAR(atoms)
>>> qsar.monoatomic(R1=3.0)
>>> print "average CN is ", qsar.CN
"""
self.chems = ['*'] # any element. For now used for report only
N = len(self.atoms)
nl = NeighborList( [0.5 * R1] * N, self_interaction=False, bothways=True )
nl.build(self.atoms)
CN = 0
Ncore = 0
Nshell = 0
CNshell = 0 # average CN of surface atoms
for i in xrange(0, N):
indeces, offsets = nl.get_neighbors(i)
CN += len(indeces)
if len(indeces) < 12:
Nshell += 1
CNshell += len(indeces)
else:
Ncore += 1
CN = CN * 1.0 / N
CNshell = CNshell * 1.0 / Nshell
#atoms.center()
R = self.atoms.positions.max() / 2.0
if calc_energy:
#from asap3 import EMT
from ase.calculators.emt import EMT
atoms.set_calculator(EMT())
E = atoms.get_potential_energy()
else:
E = -1
#return N, R, CN, E, Ncore, CNshell
self.N = N #TODO: use array property CNs
self.R = R
self.CN = CN
self.CNs = np.array([[CN]])
self.E = E
self.Ncore = Ncore
self.CNshell = CNshell
def __init__(self, bopatoms: BOPAtoms, cutoffs: list, **kwargs):
self.bopatoms = bopatoms
self.nl = NeighborList(cutoffs=cutoffs, bothways=True, self_interaction=False, **kwargs)
self.nl.update(bopatoms)
class EAM(Calculator):
r"""
EAM Interface Documentation
Introduction
============
The Embedded Atom Method (EAM) [1]_ is a classical potential which is
good for modelling metals, particularly fcc materials. Because it is
an equiaxial potential the EAM does not model directional bonds
well. However, the Angular Dependent Potential (ADP) [2]_ which is an
extended version of EAM is able to model directional bonds and is also
included in the EAM calculator.
Generally all that is required to use this calculator is to supply a
potential file or as a set of functions that describe the potential.
The files containing the potentials for this calculator are not
included but many suitable potentials can be downloaded from The
Interatomic Potentials Repository Project at
http://www.ctcms.nist.gov/potentials/
Theory
======
A single element EAM potential is defined by three functions: the
embedded energy, electron density and the pair potential. A two
element alloy contains the individual three functions for each element
plus cross pair interactions. The ADP potential has two additional
sets of data to define the dipole and quadrupole directional terms for
each alloy and their cross interactions.
The total energy `E_{\rm tot}` of an arbitrary arrangement of atoms is
given by the EAM potential as
.. math::
E_\text{tot} = \sum_i F(\bar\rho_i) + \frac{1}{2}\sum_{i\ne j} \phi(r_{ij})
and
.. math::
\bar\rho_i = \sum_j \rho(r_{ij})
where `F` is an embedding function, namely the energy to embed an atom `i` in
the combined electron density `\bar\rho_i` which is contributed from
each of its neighbouring atoms `j` by an amount `\rho(r_{ij})`,
`\phi(r_{ij})` is the pair potential function representing the energy
in bond `ij` which is due to the short-range electro-static
interaction between atoms, and `r_{ij}` is the distance between an
atom and its neighbour for that bond.
The ADP potential is defined as
.. math::
E_\text{tot} = \sum_i F(\bar\rho_i) + \frac{1}{2}\sum_{i\ne j} \phi(r_{ij})
+ \frac{1}{2} \sum_{i,\alpha} (\mu_i^\alpha)^2
+ \frac{1}{2} \sum_{i,\alpha,\beta} (\lambda_i^{\alpha\beta})^2
- \frac{1}{6} \sum_i \nu_i^2
where `\mu_i^\alpha` is the dipole vector, `\lambda_i^{\alpha\beta}`
is the quadrupole tensor and `\nu_i` is the trace of
`\lambda_i^{\alpha\beta}`.
Running the Calculator
======================
EAM calculates the cohesive atom energy and forces. Internally the
potential functions are defined by splines which may be directly
supplied or created by reading the spline points from a data file from
which a spline function is created. The LAMMPS compatible ``.alloy``
and ``.adp`` formats are supported. The LAMMPS ``.eam`` format is
slightly different from the ``.alloy`` format and is currently not
supported.
For example::
from ase.calculators.eam import EAM
mishin = EAM(potential='Al99.eam.alloy')
mishin.write_potential('new.eam.alloy')
mishin.plot()
slab.set_calculator(mishin)
slab.get_potential_energy()
slab.get_forces()
The breakdown of energy contribution from the indvidual components are
stored in the calculator instance ``.results['energy_components']``
Arguments
=========
========================= ====================================================
Keyword Description
========================= ====================================================
``potential`` file of potential in ``.alloy`` or ``.adp`` format
(This is generally all you need to supply)
``elements[N]`` array of N element abbreviations
``embedded_energy[N]`` arrays of embedded energy functions
``electron_density[N]`` arrays of electron density functions
``phi[N,N]`` arrays of pair potential functions
``d_embedded_energy[N]`` arrays of derivative embedded energy functions
``d_electron_density[N]`` arrays of derivative electron density functions
``d_phi[N,N]`` arrays of derivative pair potentials functions
``d[N,N], q[N,N]`` ADP dipole and quadrupole function
``d_d[N,N], d_q[N,N]`` ADP dipole and quadrupole derivative functions
``skin`` skin distance passed to NeighborList(). If no atom
has moved more than the skin-distance since the last
call to the ``update()`` method then the neighbor
list can be reused. Defaults to 1.0.
``form`` the form of the potential ``alloy`` or ``adp``. This
will be determined from the file suffix or must be
set if using equations
========================= ====================================================
Additional parameters for writing potential files
=================================================
The following parameters are only required for writing a potential in
``.alloy`` or ``.adp`` format file.
========================= ====================================================
Keyword Description
========================= ====================================================
``header`` Three line text header. Default is standard message.
``Z[N]`` Array of atomic number of each element
``mass[N]`` Atomic mass of each element
``a[N]`` Array of lattice parameters for each element
``lattice[N]`` Lattice type
``nrho`` No. of rho samples along embedded energy curve
``drho`` Increment for sampling density
``nr`` No. of radial points along density and pair
potential curves
``dr`` Increment for sampling radius
========================= ====================================================
Special features
================
``.plot()``
Plots the individual functions. This may be called from multiple EAM
potentials to compare the shape of the individual curves. This
function requires the installation of the Matplotlib libraries.
Notes/Issues
=============
* Although currently not fast, this calculator can be good for trying
small calculations or for creating new potentials by matching baseline
data such as from DFT results. The format for these potentials is
compatible with LAMMPS_ and so can be used either directly by LAMMPS or
with the ASE LAMMPS calculator interface.
* Supported formats are the LAMMPS_ ``.alloy`` and ``.adp``. The
``.eam`` format is currently not supported. The form of the
potential will be determined from the file suffix.
* Any supplied values will override values read from the file.
* The derivative functions, if supplied, are only used to calculate
forces.
* There is a bug in early versions of scipy that will cause eam.py to
crash when trying to evaluate splines of a potential with one
neighbor such as caused by evaluating a dimer.
.. _LAMMPS: http://lammps.sandia.gov/
.. [1] M.S. Daw and M.I. Baskes, Phys. Rev. Letters 50 (1983)
1285.
.. [2] Y. Mishin, M.J. Mehl, and D.A. Papaconstantopoulos,
Acta Materialia 53 2005 4029--4041.
End EAM Interface Documentation
"""
implemented_properties = ['energy', 'forces']
default_parameters = dict(
skin=1.0,
potential=None,
header=[b'EAM/ADP potential file\n',
b'Generated from eam.py\n',
b'blank\n'])
def __init__(self, restart=None, ignore_bad_restart_file=False,
label=os.curdir, atoms=None, **kwargs):
if 'potential' in kwargs:
self.read_potential(kwargs['potential'])
Calculator.__init__(self, restart, ignore_bad_restart_file,
label, atoms, **kwargs)
valid_args = ('potential', 'elements', 'header', 'drho', 'dr',
'cutoff', 'atomic_number', 'mass', 'a', 'lattice',
'embedded_energy', 'electron_density', 'phi',
# derivatives
'd_embedded_energy', 'd_electron_density', 'd_phi',
'd', 'q', 'd_d', 'd_q', # adp terms
'skin', 'form', 'Z', 'nr', 'nrho', 'mass')
# set any additional keyword arguments
for arg, val in self.parameters.items():
if arg in valid_args:
setattr(self, arg, val)
else:
raise RuntimeError('unknown keyword arg "%s" : not in %s'
% (arg, valid_args))
def set_form(self, fileobj):
"""set the form variable based on the file name suffix"""
extension = os.path.splitext(fileobj)[1]
if extension == '.eam':
self.form = 'eam'
elif extension == '.alloy':
self.form = 'alloy'
elif extension == '.adp':
self.form = 'adp'
else:
raise RuntimeError('unknown file extension type: %s' % extension)
def read_potential(self, fileobj):
"""Reads a LAMMPS EAM file in alloy or adp format
and creates the interpolation functions from the data
"""
if isinstance(fileobj, basestring):
f = open(fileobj)
self.set_form(fileobj)
else:
f = fileobj
def lines_to_list(lines):
"""Make the data one long line so as not to care how its formatted
"""
data = []
for line in lines:
data.extend(line.split())
return data
lines = f.readlines()
if self.form == 'eam': # single element eam file (aka funcfl)
self.header = lines[:1]
data = lines_to_list(lines[1:])
# eam form is just like an alloy form for one element
self.Nelements = 1
self.Z = np.array([data[0]], dtype=int)
self.mass = np.array([data[1]])
self.a = np.array([data[2]])
self.lattice = [data[3]]
self.nrho = int(data[4])
self.drho = float(data[5])
self.nr = int(data[6])
self.dr = float(data[7])
self.cutoff = float(data[8])
n = 9 + self.nrho
self.embedded_data = np.array([np.float_(data[9:n])])
self.rphi_data = np.zeros([self.Nelements, self.Nelements,
self.nr])
effective_charge = np.float_(data[n:n + self.nr])
# convert effective charges to rphi according to
# http://lammps.sandia.gov/doc/pair_eam.html
self.rphi_data[0, 0] = Bohr * Hartree * (effective_charge**2)
self.density_data = np.array(
[np.float_(data[n + self.nr:n + 2 * self.nr])])
else:
self.header = lines[:3]
i = 3
data = lines_to_list(lines[i:])
self.Nelements = int(data[0])
d = 1
self.elements = data[d:d + self.Nelements]
d += self.Nelements
self.nrho = int(data[d])
self.drho = float(data[d + 1])
self.nr = int(data[d + 2])
self.dr = float(data[d + 3])
self.cutoff = float(data[d + 4])
self.embedded_data = np.zeros([self.Nelements, self.nrho])
self.density_data = np.zeros([self.Nelements, self.nr])
self.Z = np.zeros([self.Nelements], dtype=int)
self.mass = np.zeros([self.Nelements])
self.a = np.zeros([self.Nelements])
self.lattice = []
d += 5
# reads in the part of the eam file for each element
for elem in range(self.Nelements):
self.Z[elem] = int(data[d])
self.mass[elem] = float(data[d + 1])
self.a[elem] = float(data[d + 2])
self.lattice.append(data[d + 3])
d += 4
self.embedded_data[elem] = np.float_(
data[d:(d + self.nrho)])
d += self.nrho
self.density_data[elem] = np.float_(data[d:(d + self.nr)])
d += self.nr
# reads in the r*phi data for each interaction between elements
self.rphi_data = np.zeros([self.Nelements, self.Nelements,
self.nr])
for i in range(self.Nelements):
for j in range(i + 1):
self.rphi_data[j, i] = np.float_(data[d:(d + self.nr)])
d += self.nr
self.r = np.arange(0, self.nr) * self.dr
self.rho = np.arange(0, self.nrho) * self.drho
self.set_splines()
if (self.form == 'adp'):
self.read_adp_data(data, d)
self.set_adp_splines()
def set_splines(self):
# this section turns the file data into three functions (and
# derivative functions) that define the potential
self.embedded_energy = np.empty(self.Nelements, object)
self.electron_density = np.empty(self.Nelements, object)
self.d_embedded_energy = np.empty(self.Nelements, object)
self.d_electron_density = np.empty(self.Nelements, object)
for i in range(self.Nelements):
self.embedded_energy[i] = spline(self.rho,
self.embedded_data[i], k=3)
self.electron_density[i] = spline(self.r,
self.density_data[i], k=3)
self.d_embedded_energy[i] = self.deriv(self.embedded_energy[i])
self.d_electron_density[i] = self.deriv(self.electron_density[i])
self.phi = np.empty([self.Nelements, self.Nelements], object)
self.d_phi = np.empty([self.Nelements, self.Nelements], object)
# ignore the first point of the phi data because it is forced
# to go through zero due to the r*phi format in alloy and adp
for i in range(self.Nelements):
for j in range(i, self.Nelements):
self.phi[i, j] = spline(
self.r[1:],
self.rphi_data[i, j][1:] / self.r[1:], k=3)
self.d_phi[i, j] = self.deriv(self.phi[i, j])
if j != i:
self.phi[j, i] = self.phi[i, j]
self.d_phi[j, i] = self.d_phi[i, j]
def set_adp_splines(self):
self.d = np.empty([self.Nelements, self.Nelements], object)
self.d_d = np.empty([self.Nelements, self.Nelements], object)
self.q = np.empty([self.Nelements, self.Nelements], object)
self.d_q = np.empty([self.Nelements, self.Nelements], object)
for i in range(self.Nelements):
for j in range(i, self.Nelements):
self.d[i, j] = spline(self.r[1:], self.d_data[i, j][1:], k=3)
self.d_d[i, j] = self.deriv(self.d[i, j])
self.q[i, j] = spline(self.r[1:], self.q_data[i, j][1:], k=3)
self.d_q[i, j] = self.deriv(self.q[i, j])
# make symmetrical
if j != i:
self.d[j, i] = self.d[i, j]
self.d_d[j, i] = self.d_d[i, j]
self.q[j, i] = self.q[i, j]
self.d_q[j, i] = self.d_q[i, j]
def read_adp_data(self, data, d):
"""read in the extra adp data from the potential file"""
self.d_data = np.zeros([self.Nelements, self.Nelements, self.nr])
# should be non symmetrical combinations of 2
for i in range(self.Nelements):
for j in range(i + 1):
self.d_data[j, i] = data[d:d + self.nr]
d += self.nr
self.q_data = np.zeros([self.Nelements, self.Nelements, self.nr])
# should be non symmetrical combinations of 2
for i in range(self.Nelements):
for j in range(i + 1):
self.q_data[j, i] = data[d:d + self.nr]
d += self.nr
def write_potential(self, filename, nc=1, numformat='%.8e'):
"""Writes out the potential in the format given by the form
variable to 'filename' with a data format that is nc columns
wide. Note: array lengths need to be an exact multiple of nc
"""
f = open(filename, 'wb')
assert self.nr % nc == 0
assert self.nrho % nc == 0
for line in self.header:
f.write(line)
f.write('{0} '.format(self.Nelements).encode())
f.write(' '.join(self.elements).encode() + b'\n')
f.write(('%d %f %d %f %f \n' %
(self.nrho, self.drho, self.nr,
self.dr, self.cutoff)).encode())
# start of each section for each element
# rs = np.linspace(0, self.nr * self.dr, self.nr)
# rhos = np.linspace(0, self.nrho * self.drho, self.nrho)
rs = np.arange(0, self.nr) * self.dr
rhos = np.arange(0, self.nrho) * self.drho
for i in range(self.Nelements):
f.write(('%d %f %f %s\n' %
(self.Z[i], self.mass[i],
self.a[i], str(self.lattice[i]))).encode())
np.savetxt(f,
self.embedded_energy[i](rhos).reshape(self.nrho // nc,
nc),
fmt=nc * [numformat])
np.savetxt(f,
self.electron_density[i](rs).reshape(self.nr // nc,
nc),
fmt=nc * [numformat])
# write out the pair potentials in Lammps DYNAMO setfl format
# as r*phi for alloy format
for i in range(self.Nelements):
for j in range(i, self.Nelements):
np.savetxt(f,
(rs * self.phi[i, j](rs)).reshape(self.nr // nc,
nc),
fmt=nc * [numformat])
if self.form == 'adp':
# these are the u(r) or dipole values
for i in range(self.Nelements):
for j in range(i + 1):
np.savetxt(f, self.d_data[i, j])
# these are the w(r) or quadrupole values
for i in range(self.Nelements):
for j in range(i + 1):
np.savetxt(f, self.q_data[i, j])
f.close()
def update(self, atoms):
# check all the elements are available in the potential
self.Nelements = len(self.elements)
elements = np.unique(atoms.get_chemical_symbols())
unavailable = np.logical_not(
np.array([item in self.elements for item in elements]))
if np.any(unavailable):
raise RuntimeError('These elements are not in the potential: %s' %
elements[unavailable])
# cutoffs need to be a vector for NeighborList
cutoffs = self.cutoff * np.ones(len(atoms))
# convert the elements to an index of the position
# in the eam format
self.index = np.array([self.elements.index(el)
for el in atoms.get_chemical_symbols()])
self.pbc = atoms.get_pbc()
# since we need the contribution of all neighbors to the
# local electron density we cannot just calculate and use
# one way neighbors
self.neighbors = NeighborList(cutoffs,
skin=self.parameters.skin,
self_interaction=False,
bothways=True)
self.neighbors.update(atoms)
def calculate(self, atoms=None, properties=['energy'],
system_changes=all_changes):
"""EAM Calculator
atoms: Atoms object
Contains positions, unit-cell, ...
properties: list of str
List of what needs to be calculated. Can be any combination
of 'energy', 'forces'
system_changes: list of str
List of what has changed since last calculation. Can be
any combination of these five: 'positions', 'numbers', 'cell',
'pbc', 'initial_charges' and 'initial_magmoms'.
"""
Calculator.calculate(self, atoms, properties, system_changes)
# we shouldn't really recalc if charges or magmos change
if len(system_changes) > 0: # something wrong with this way
self.update(self.atoms)
self.calculate_energy(self.atoms)
if 'forces' in properties:
self.calculate_forces(self.atoms)
# check we have all the properties requested
for property in properties:
if property not in self.results:
if property is 'energy':
self.calculate_energy(self.atoms)
if property is 'forces':
self.calculate_forces(self.atoms)
# we need to remember the previous state of parameters
# if 'potential' in parameter_changes and potential != None:
# self.read_potential(potential)
def calculate_energy(self, atoms):
"""Calculate the energy
the energy is made up of the ionic or pair interaction and
the embedding energy of each atom into the electron cloud
generated by its neighbors
"""
pair_energy = 0.0
embedding_energy = 0.0
mu_energy = 0.0
lam_energy = 0.0
trace_energy = 0.0
self.total_density = np.zeros(len(atoms))
if (self.form == 'adp'):
self.mu = np.zeros([len(atoms), 3])
self.lam = np.zeros([len(atoms), 3, 3])
for i in range(len(atoms)): # this is the atom to be embedded
neighbors, offsets = self.neighbors.get_neighbors(i)
offset = np.dot(offsets, atoms.get_cell())
rvec = (atoms.positions[neighbors] + offset -
atoms.positions[i])
# calculate the distance to the nearest neighbors
r = np.sqrt(np.sum(np.square(rvec), axis=1)) # fast
# r = np.apply_along_axis(np.linalg.norm, 1, rvec) # sloow
nearest = np.arange(len(r))[r <= self.cutoff]
for j_index in range(self.Nelements):
use = self.index[neighbors[nearest]] == j_index
if not use.any():
continue
pair_energy += np.sum(self.phi[self.index[i], j_index](
r[nearest][use])) / 2.
density = np.sum(
self.electron_density[j_index](r[nearest][use]))
self.total_density[i] += density
if self.form == 'adp':
self.mu[i] += self.adp_dipole(
r[nearest][use],
rvec[nearest][use],
self.d[self.index[i], j_index])
self.lam[i] += self.adp_quadrupole(
r[nearest][use],
rvec[nearest][use],
self.q[self.index[i], j_index])
# add in the electron embedding energy
embedding_energy += self.embedded_energy[self.index[i]](
self.total_density[i])
components = dict(pair=pair_energy, embedding=embedding_energy)
if self.form == 'adp':
mu_energy += np.sum(self.mu ** 2) / 2.
lam_energy += np.sum(self.lam ** 2) / 2.
for i in range(len(atoms)): # this is the atom to be embedded
trace_energy -= np.sum(self.lam[i].trace() ** 2) / 6.
adp_result = dict(adp_mu=mu_energy,
adp_lam=lam_energy,
adp_trace=trace_energy)
components.update(adp_result)
self.positions = atoms.positions.copy()
self.cell = atoms.get_cell().copy()
energy = 0.0
for i in components.keys():
energy += components[i]
self.energy_free = energy
self.energy_zero = energy
self.results['energy_components'] = components
self.results['energy'] = energy
def calculate_forces(self, atoms):
# calculate the forces based on derivatives of the three EAM functions
self.update(atoms)
self.results['forces'] = np.zeros((len(atoms), 3))
for i in range(len(atoms)): # this is the atom to be embedded
neighbors, offsets = self.neighbors.get_neighbors(i)
offset = np.dot(offsets, atoms.get_cell())
# create a vector of relative positions of neighbors
rvec = atoms.positions[neighbors] + offset - atoms.positions[i]
r = np.sqrt(np.sum(np.square(rvec), axis=1))
nearest = np.arange(len(r))[r < self.cutoff]
d_embedded_energy_i = self.d_embedded_energy[
self.index[i]](self.total_density[i])
urvec = rvec.copy() # unit directional vector
for j in np.arange(len(neighbors)):
urvec[j] = urvec[j] / r[j]
for j_index in range(self.Nelements):
use = self.index[neighbors[nearest]] == j_index
if not use.any():
continue
rnuse = r[nearest][use]
density_j = self.total_density[neighbors[nearest][use]]
scale = (self.d_phi[self.index[i], j_index](rnuse) +
(d_embedded_energy_i *
self.d_electron_density[j_index](rnuse)) +
(self.d_embedded_energy[j_index](density_j) *
self.d_electron_density[self.index[i]](rnuse)))
self.results['forces'][i] += np.dot(scale, urvec[nearest][use])
if (self.form == 'adp'):
adp_forces = self.angular_forces(
self.mu[i],
self.mu[neighbors[nearest][use]],
self.lam[i],
self.lam[neighbors[nearest][use]],
rnuse,
rvec[nearest][use],
self.index[i],
j_index)
self.results['forces'][i] += adp_forces
def angular_forces(self, mu_i, mu, lam_i, lam, r, rvec, form1, form2):
# calculate the extra components for the adp forces
# rvec are the relative positions to atom i
psi = np.zeros(mu.shape)
for gamma in range(3):
term1 = (mu_i[gamma] - mu[:, gamma]) * self.d[form1][form2](r)
term2 = np.sum((mu_i - mu) *
self.d_d[form1][form2](r)[:, np.newaxis] *
(rvec * rvec[:, gamma][:, np.newaxis] /
r[:, np.newaxis]), axis=1)
term3 = 2 * np.sum((lam_i[:, gamma] + lam[:, :, gamma]) *
rvec * self.q[form1][form2](r)[:, np.newaxis],
axis=1)
term4 = 0.0
for alpha in range(3):
for beta in range(3):
rs = rvec[:, alpha] * rvec[:, beta] * rvec[:, gamma]
term4 += ((lam_i[alpha, beta] + lam[:, alpha, beta]) *
self.d_q[form1][form2](r) * rs) / r
term5 = ((lam_i.trace() + lam.trace(axis1=1, axis2=2)) *
(self.d_q[form1][form2](r) * r +
2 * self.q[form1][form2](r)) * rvec[:, gamma]) / 3.
# the minus for term5 is a correction on the adp
# formulation given in the 2005 Mishin Paper and is posted
# on the NIST website with the AlH potential
psi[:, gamma] = term1 + term2 + term3 + term4 - term5
return np.sum(psi, axis=0)
def adp_dipole(self, r, rvec, d):
# calculate the dipole contribution
mu = np.sum((rvec * d(r)[:, np.newaxis]), axis=0)
return mu # sign to agree with lammps
def adp_quadrupole(self, r, rvec, q):
# slow way of calculating the quadrupole contribution
r = np.sqrt(np.sum(rvec ** 2, axis=1))
lam = np.zeros([rvec.shape[0], 3, 3])
qr = q(r)
for alpha in range(3):
for beta in range(3):
lam[:, alpha, beta] += qr * rvec[:, alpha] * rvec[:, beta]
return np.sum(lam, axis=0)
def deriv(self, spline):
"""Wrapper for extracting the derivative from a spline"""
def d_spline(aspline):
return spline(aspline, 1)
return d_spline
def plot(self, name=''):
"""Plot the individual curves"""
try:
import matplotlib.pyplot as plt
except ImportError:
raise NotAvailable('This needs matplotlib module.')
if self.form == 'eam' or self.form == 'alloy':
nrow = 2
elif self.form == 'adp':
nrow = 3
else:
raise RuntimeError('Unknown form of potential: %s' % self.form)
if hasattr(self, 'r'):
r = self.r
else:
r = np.linspace(0, self.cutoff, 50)
if hasattr(self, 'rho'):
rho = self.rho
else:
rho = np.linspace(0, 10.0, 50)
plt.subplot(nrow, 2, 1)
self.elem_subplot(rho, self.embedded_energy,
r'$\rho$', r'Embedding Energy $F(\bar\rho)$',
name, plt)
plt.subplot(nrow, 2, 2)
self.elem_subplot(r, self.electron_density,
r'$r$', r'Electron Density $\rho(r)$', name, plt)
plt.subplot(nrow, 2, 3)
self.multielem_subplot(r, self.phi,
r'$r$', r'Pair Potential $\phi(r)$', name, plt)
plt.ylim(-1.0, 1.0) # need reasonable values
if self.form == 'adp':
plt.subplot(nrow, 2, 5)
self.multielem_subplot(r, self.d,
r'$r$', r'Dipole Energy', name, plt)
plt.subplot(nrow, 2, 6)
self.multielem_subplot(r, self.q,
r'$r$', r'Quadrupole Energy', name, plt)
plt.plot()
def elem_subplot(self, curvex, curvey, xlabel, ylabel, name, plt):
plt.xlabel(xlabel)
plt.ylabel(ylabel)
for i in np.arange(self.Nelements):
label = name + ' ' + self.elements[i]
plt.plot(curvex, curvey[i](curvex), label=label)
plt.legend()
def multielem_subplot(self, curvex, curvey, xlabel, ylabel, name, plt):
plt.xlabel(xlabel)
plt.ylabel(ylabel)
for i in np.arange(self.Nelements):
for j in np.arange(i + 1):
label = name + ' ' + self.elements[i] + '-' + self.elements[j]
plt.plot(curvex, curvey[i, j](curvex), label=label)
plt.legend()
def calculate(self, crystal, system=None):
"""The symmetry functions are obtained through this `calculate` method.
Parameters
----------
crystal: object
ASE Structure object.
system: list
A list of the crystal structures system.
All elements in the list have to be integer. For example, the
system of crystal structure is NaCl system. Then, system should be
pass as [11, 17]
Returns
-------
all_G: dict
The user-defined symmetry functions that represent the crystal.
Currently, there are 3 types of symmetry functions implemented.
Here are the order of the descriptors are printed out based on
their symmetry parameters:
- G2: ["element", "Rs", "eta"]
- G4: ["pair_elements", "eta", "lambda", "zeta"]
- G5: ["pair_elements", "eta", "lambda", "zeta"]
"""
self.crystal = crystal
atomic_numbers = np.array(crystal.get_atomic_numbers())
vol = crystal.get_volume()
if system is None:
type_set1 = create_type_set(atomic_numbers, 1) # l
type_set2 = create_type_set(atomic_numbers, 2) # l
else:
system = np.array(system, dtype=int)
type_set1 = create_type_set(system, 1) # l
type_set2 = create_type_set(system, 2) # l
# Initialize dict for the symmetry functions
self.all_G = {'x': [], 'elements': []}
if self.derivative:
self.all_G['dxdr'] = None
self.all_G['seq'] = None
if self.stress:
self.all_G['rdxdr'] = None
# Obtain neighbors info.
rc = [self.Rc / 2] * len(self.crystal)
neighbors = NeighborList(rc,
self_interaction=False,
bothways=True,
skin=0.0)
neighbors.update(crystal)
for i in range(len(crystal)):
element = crystal.get_chemical_symbols()[i]
indices, offsets = neighbors.get_neighbors(i)
assert len(indices)>0, \
f"There's no neighbor for this structure at Rc = {self.Rc} A."
Ri = crystal.get_positions()[i]
total_neighbors = len(
indices) # total number of neighbors of atom i
Rj = np.zeros([total_neighbors, 3])
Dij = np.zeros(total_neighbors)
IDs = np.zeros(total_neighbors, dtype=int)
jks = np.array(list(combinations(range(total_neighbors), 2)))
count = 0
for j, offset in zip(indices, offsets):
Rj[count, :] = crystal.positions[j] + np.dot(
offset, crystal.get_cell())
Dij[count] = np.sqrt(sum((Rj[count, :] - Ri)**2))
IDs[count] = j
count += 1
Rij = Rj - Ri
Gi = []
GiPrime = None
GiPrime_seq = None
if self.G2_parameters is not None:
G2i = calculate_G2(Dij, IDs, atomic_numbers, type_set1,
self.Rc, self.G2_parameters, self._type)
Gi = np.append(Gi, G2i)
if self.derivative:
seq, G2iP, rG2iP = calculate_G2Prime(
Rij, Ri, i, IDs, atomic_numbers, type_set1, self.Rc,
self.G2_parameters, self._type)
if GiPrime is None:
GiPrime = G2iP #[N1, l, 3]
GiPrime_seq = seq
if self.stress:
rGiPrime = rG2iP
else:
GiPrime_seq = np.append(GiPrime_seq, seq, axis=0)
GiPrime = np.append(GiPrime, G2iP, axis=1)
if self.stress:
rGiPrime = np.append(rGiPrime, rG2iP, axis=1)
if self.G4_parameters is not None:
G4i = calculate_G4(Rij, IDs, jks, atomic_numbers, type_set2,
self.Rc, self.G4_parameters, self._type)
Gi = np.append(Gi, G4i)
if self.derivative:
seq, G4iP, rG4iP = calculate_G4Prime(
Rij, Ri, i, IDs, jks, atomic_numbers, type_set2,
self.Rc, self.G4_parameters, self._type)
if GiPrime is None:
GiPrime = G4iP
GiPrime_seq = seq
if self.stress:
rGiPrime = rG4iP
else:
#GiPrime_seq = np.append(GiPrime_seq, seq, axis=0)
GiPrime = np.append(GiPrime, G4iP, axis=1)
if self.stress:
rGiPrime = np.append(rGiPrime, rG4iP, axis=1)
#print(seq.shape, G4iP.shape, rG4iP.shape)
#print(GiPrime_seq.shape, GiPrime.shape, rGiPrime.shape)
if self.G5_parameters is not None:
G5i = calculate_G5(Rij, IDs, jks, atomic_numbers, type_set2,
self.Rc, self.G5_parameters, self._type)
Gi = np.append(Gi, G5i)
if self.derivative:
seq, G5iP, rG5iP = calculate_G5Prime(
Rij, Ri, i, IDs, jks, atomic_numbers, type_set2,
self.Rc, self.G5_parameters, self._type)
if GiPrime is None:
GiPrime = G5iP
GiPrime_seq = seq
if self.stress:
rGiPrime = rG5iP
else:
GiPrime = np.append(GiPrime, G5iP, axis=1)
if self.stress:
rGiPrime = np.append(rGiPrime, rG5iP, axis=1)
self.all_G['x'].append(Gi)
self.all_G['elements'].append(element)
if self.derivative:
if self.all_G['seq'] is None:
self.all_G['seq'] = GiPrime_seq
self.all_G['dxdr'] = GiPrime
if self.stress:
self.all_G['rdxdr'] = rGiPrime
else:
self.all_G['seq'] = np.append(self.all_G['seq'],
GiPrime_seq,
axis=0)
self.all_G['dxdr'] = np.append(self.all_G['dxdr'],
GiPrime,
axis=0)
if self.stress:
self.all_G['rdxdr'] = np.append(self.all_G['rdxdr'],
rGiPrime,
axis=0)
self.all_G['x'] = np.asarray(self.all_G['x'])
if self.derivative:
self.all_G['dxdr'] = np.asarray(self.all_G['dxdr'])
self.all_G['seq'] = np.asarray(self.all_G['seq'])
if self.stress:
self.all_G['rdxdr'] = -np.asarray(self.all_G['rdxdr']) / vol
else:
self.all_G['rdxdr'] = None
return self.all_G
def calculate(self, atoms=None,
properties=['energy'],
system_changes=all_changes):
Calculator.calculate(self, atoms, properties, system_changes)
natoms = len(self.atoms)
sigma = self.parameters.sigma
epsilon = self.parameters.epsilon
tolerAngs = self.parameters.tolerAngs
tolerMult = self.parameters.tolerMult
cutoff = self.parameters.cutoff
if cutoff is None:
cutoff = 0.9
if 'numbers' in system_changes:
self.nl = NeighborList([cutoff / 2] * natoms,\
self_interaction=False)
self.nl.update(self.atoms)
positions = self.atoms.positions
cell = self.atoms.cell
e0 = 4 * epsilon * ((sigma / cutoff)**12 - (sigma / cutoff)**6)
energy = 0.0
forces = np.zeros((natoms, 3))
stress = np.zeros((3, 3))
def getLJparam(elem1, elem2):
sigma_tmp = covalRadii[elem1] + covalRadii[elem1]
return sigma_tmp
for a1 in range(natoms):
neighbors, offsets = self.nl.get_neighbors(a1)
cells = np.dot(offsets, cell)
d = positions[neighbors] + cells - positions[a1]
r2 = (d**2).sum(1)
covalBl = covalRadii[self.atoms.get_atomic_numbers()[a1]]+\
covalRadii[self.atoms.get_atomic_numbers()[neighbors]]
c6 = (sigma**2 / r2)**3
c6[covalBl - np.sqrt(r2) < tolerAngs] = 0.0
c6[np.sqrt(r2) / covalBl > 1 - tolerMult] = 0.0
# c6[r2 > radius**2] = 0.0
energy -= e0 * (c6 != 0.0).sum()
c12 = c6**2
energy += 4 * epsilon * (c12 - c6).sum()
f = (24 * epsilon * (2 * c12 - c6) / r2)[:, np.newaxis] * d
forces[a1] -= f.sum(axis=0)
for a2, f2 in zip(neighbors, f):
forces[a2] += f2
stress += np.dot(f.T, d)
if 'stress' in properties:
if self.atoms.number_of_lattice_vectors == 3:
stress += stress.T.copy()
stress *= -0.5 / self.atoms.get_volume()
self.results['stress'] = stress.flat[[0, 4, 8, 5, 2, 1]]
else:
raise PropertyNotImplementedError
self.results['energy'] = energy
self.results['free_energy'] = energy
self.results['forces'] = forces
class OPLSff:
def __init__(self, fileobj=None, warnings=0):
self.warnings = warnings
self.data = {}
if fileobj is not None:
self.read(fileobj)
def read(self, fileobj, comments='#'):
if isinstance(fileobj, str):
fileobj = open(fileobj)
def read_block(name, symlen, nvalues):
"""Read a data block.
name: name of the block to store in self.data
symlen: length of the symbol
nvalues: number of values expected
"""
if name not in self.data:
self.data[name] = {}
data = self.data[name]
def add_line():
line = fileobj.readline().strip()
if not len(line): # end of the block
return False
line = line.split('#')[0] # get rid of comments
if len(line) > symlen:
symbol = line[:symlen]
words = line[symlen:].split()
if len(words) >= nvalues:
if nvalues == 1:
data[symbol] = float(words[0])
else:
data[symbol] = [
float(word) for word in words[:nvalues]
]
return True
while add_line():
pass
read_block('one', 2, 3)
read_block('bonds', 5, 2)
read_block('angles', 8, 2)
read_block('dihedrals', 11, 4)
read_block('cutoffs', 5, 1)
self.bonds = BondData(self.data['bonds'])
self.angles = AnglesData(self.data['angles'])
self.dihedrals = DihedralsData(self.data['dihedrals'])
self.cutoffs = CutoffList(self.data['cutoffs'])
def write_lammps(self, atoms, prefix='lammps'):
"""Write input for a LAMMPS calculation."""
self.prefix = prefix
if hasattr(atoms, 'connectivities'):
connectivities = atoms.connectivities
else:
btypes, blist = self.get_bonds(atoms)
atypes, alist = self.get_angles()
dtypes, dlist = self.get_dihedrals(alist, atypes)
connectivities = {
'bonds': blist,
'bond types': btypes,
'angles': alist,
'angle types': atypes,
'dihedrals': dlist,
'dihedral types': dtypes
}
self.write_lammps_definitions(atoms, btypes, atypes, dtypes)
self.write_lammps_in()
self.write_lammps_atoms(atoms, connectivities)
def write_lammps_in(self):
fileobj = self.prefix + '_in'
if isinstance(fileobj, str):
fileobj = open(fileobj, 'w')
fileobj.write("""# LAMMPS relaxation (written by ASE)
units metal
atom_style full
boundary p p p
#boundary p p f
""")
fileobj.write('read_data ' + self.prefix + '_atoms\n')
fileobj.write('include ' + self.prefix + '_opls\n')
fileobj.write("""
kspace_style pppm 1e-5
#kspace_modify slab 3.0
neighbor 1.0 bin
neigh_modify delay 0 every 1 check yes
thermo 1000
thermo_style custom step temp press cpu pxx pyy pzz pxy pxz pyz ke pe etotal vol lx ly lz atoms
dump 1 all xyz 1000 dump_relax.xyz
dump_modify 1 sort id
restart 100000 test_relax
min_style fire
minimize 1.0e-14 1.0e-5 100000 100000
""")
fileobj.close()
def write_lammps_atoms(self, atoms, connectivities):
"""Write atoms input for LAMMPS"""
fname = self.prefix + '_atoms'
fileobj = open(fname, 'w')
# header
fileobj.write(fileobj.name + ' (by ' + str(self.__class__) + ')\n\n')
fileobj.write(str(len(atoms)) + ' atoms\n')
fileobj.write(str(len(atoms.types)) + ' atom types\n')
blist = connectivities['bonds']
if len(blist):
btypes = connectivities['bond types']
fileobj.write(str(len(blist)) + ' bonds\n')
fileobj.write(str(len(btypes)) + ' bond types\n')
alist = connectivities['angles']
if len(alist):
atypes = connectivities['angle types']
fileobj.write(str(len(alist)) + ' angles\n')
fileobj.write(str(len(atypes)) + ' angle types\n')
dlist = connectivities['dihedrals']
if len(dlist):
dtypes = connectivities['dihedral types']
fileobj.write(str(len(dlist)) + ' dihedrals\n')
fileobj.write(str(len(dtypes)) + ' dihedral types\n')
# cell
p = Prism(atoms.get_cell())
xhi, yhi, zhi, xy, xz, yz = p.get_lammps_prism_str()
fileobj.write('\n0.0 %s xlo xhi\n' % xhi)
fileobj.write('0.0 %s ylo yhi\n' % yhi)
fileobj.write('0.0 %s zlo zhi\n' % zhi)
# atoms
fileobj.write('\nAtoms\n\n')
tag = atoms.get_tags()
if atoms.has('molid'):
molid = atoms.get_array('molid')
else:
molid = [1] * len(atoms)
for i, r in enumerate(p.positions_to_lammps_strs(
atoms.get_positions())):
atype = atoms.types[tag[i]]
if len(atype) < 2:
atype = atype + ' '
q = self.data['one'][atype][2]
fileobj.write('%6d %3d %3d %s %s %s %s' %
((i + 1, molid[i], tag[i] + 1, q) + tuple(r)))
fileobj.write(' # ' + atoms.types[tag[i]] + '\n')
# velocities
velocities = atoms.get_velocities()
if velocities is not None:
fileobj.write('\nVelocities\n\n')
for i, v in enumerate(velocities):
fileobj.write('%6d %g %g %g\n' % (i + 1, v[0], v[1], v[2]))
# masses
fileobj.write('\nMasses\n\n')
for i, typ in enumerate(atoms.types):
cs = atoms.split_symbol(typ)[0]
fileobj.write(
'%6d %g # %s -> %s\n' %
(i + 1, atomic_masses[chemical_symbols.index(cs)], typ, cs))
# bonds
if len(blist):
fileobj.write('\nBonds\n\n')
for ib, bvals in enumerate(blist):
fileobj.write(
'%8d %6d %6d %6d ' %
(ib + 1, bvals[0] + 1, bvals[1] + 1, bvals[2] + 1))
try:
fileobj.write('# ' + btypes[bvals[0]])
except:
pass
fileobj.write('\n')
# angles
if len(alist):
fileobj.write('\nAngles\n\n')
for ia, avals in enumerate(alist):
fileobj.write('%8d %6d %6d %6d %6d ' %
(ia + 1, avals[0] + 1, avals[1] + 1,
avals[2] + 1, avals[3] + 1))
try:
fileobj.write('# ' + atypes[avals[0]])
except:
pass
fileobj.write('\n')
# dihedrals
if len(dlist):
fileobj.write('\nDihedrals\n\n')
for i, dvals in enumerate(dlist):
fileobj.write('%8d %6d %6d %6d %6d %6d ' %
(i + 1, dvals[0] + 1, dvals[1] + 1, dvals[2] + 1,
dvals[3] + 1, dvals[4] + 1))
try:
fileobj.write('# ' + dtypes[dvals[0]])
except:
pass
fileobj.write('\n')
def update_neighbor_list(self, atoms):
cut = 0.5 * max(self.data['cutoffs'].values())
self.nl = NeighborList([cut] * len(atoms),
skin=0,
bothways=True,
self_interaction=False)
self.nl.update(atoms)
self.atoms = atoms
def get_bonds(self, atoms):
"""Find bonds and return them and their types"""
cutoffs = CutoffList(self.data['cutoffs'])
self.update_neighbor_list(atoms)
types = atoms.get_types()
tags = atoms.get_tags()
cell = atoms.get_cell()
bond_list = []
bond_types = []
for i, atom in enumerate(atoms):
iname = types[tags[i]]
indices, offsets = self.nl.get_neighbors(i)
for j, offset in zip(indices, offsets):
if j <= i:
continue # do not double count
jname = types[tags[j]]
cut = cutoffs.value(iname, jname)
if cut is None:
if self.warnings > 1:
print('Warning: cutoff %s-%s not found' %
(iname, jname))
continue # don't have it
dist = np.linalg.norm(atom.position - atoms[j].position -
np.dot(offset, cell))
if dist > cut:
continue # too far away
name, val = self.bonds.name_value(iname, jname)
if name is None:
if self.warnings:
print('Warning: potential %s-%s not found' %
(iname, jname))
continue # don't have it
if name not in bond_types:
bond_types.append(name)
bond_list.append([bond_types.index(name), i, j])
return bond_types, bond_list
def get_angles(self, atoms=None):
cutoffs = CutoffList(self.data['cutoffs'])
if atoms is not None:
self.update_neighbor_list(atoms)
else:
atoms = self.atoms
types = atoms.get_types()
tags = atoms.get_tags()
cell = atoms.get_cell()
ang_list = []
ang_types = []
# center atom *-i-*
for i, atom in enumerate(atoms):
iname = types[tags[i]]
indicesi, offsetsi = self.nl.get_neighbors(i)
# search for first neighbor j-i-*
for j, offsetj in zip(indicesi, offsetsi):
jname = types[tags[j]]
cut = cutoffs.value(iname, jname)
if cut is None:
continue # don't have it
dist = np.linalg.norm(atom.position - atoms[j].position -
np.dot(offsetj, cell))
if dist > cut:
continue # too far away
# search for second neighbor j-i-k
for k, offsetk in zip(indicesi, offsetsi):
if k <= j:
continue # avoid double count
kname = types[tags[k]]
cut = cutoffs.value(iname, kname)
if cut is None:
continue # don't have it
dist = np.linalg.norm(atom.position -
np.dot(offsetk, cell) -
atoms[k].position)
if dist > cut:
continue # too far away
name, val = self.angles.name_value(jname, iname, kname)
if name is None:
if self.warnings > 1:
print('Warning: angles %s-%s-%s not found' %
(jname, iname, kname))
continue # don't have it
if name not in ang_types:
ang_types.append(name)
ang_list.append([ang_types.index(name), j, i, k])
return ang_types, ang_list
def get_dihedrals(self, ang_types, ang_list):
'Dihedrals derived from angles.'
cutoffs = CutoffList(self.data['cutoffs'])
atoms = self.atoms
types = atoms.get_types()
tags = atoms.get_tags()
cell = atoms.get_cell()
dih_list = []
dih_types = []
def append(name, i, j, k, l):
if name not in dih_types:
dih_types.append(name)
index = dih_types.index(name)
if (([index, i, j, k, l] not in dih_list)
and ([index, l, k, j, i] not in dih_list)):
dih_list.append([index, i, j, k, l])
for angle in ang_types:
l, i, j, k = angle
iname = types[tags[i]]
jname = types[tags[j]]
kname = types[tags[k]]
# search for l-i-j-k
indicesi, offsetsi = self.nl.get_neighbors(i)
for l, offsetl in zip(indicesi, offsetsi):
if l == j:
continue # avoid double count
lname = types[tags[l]]
cut = cutoffs.value(iname, lname)
if cut is None:
continue # don't have it
dist = np.linalg.norm(atoms[i].position - atoms[l].position -
np.dot(offsetl, cell))
if dist > cut:
continue # too far away
name, val = self.dihedrals.name_value(lname, iname, jname,
kname)
if name is None:
continue # don't have it
append(name, l, i, j, k)
# search for i-j-k-l
indicesk, offsetsk = self.nl.get_neighbors(k)
for l, offsetl in zip(indicesk, offsetsk):
if l == j:
continue # avoid double count
lname = types[tags[l]]
cut = cutoffs.value(kname, lname)
if cut is None:
continue # don't have it
dist = np.linalg.norm(atoms[k].position - atoms[l].position -
np.dot(offsetl, cell))
if dist > cut:
continue # too far away
name, val = self.dihedrals.name_value(iname, jname, kname,
lname)
if name is None:
continue # don't have it
append(name, i, j, k, l)
return dih_types, dih_list
def write_lammps_definitions(self, atoms, btypes, atypes, dtypes):
"""Write force field definitions for LAMMPS."""
fileobj = self.prefix + '_opls'
if isinstance(fileobj, str):
fileobj = open(fileobj, 'w')
fileobj.write('# OPLS potential\n')
fileobj.write('# write_lammps' +
str(time.asctime(time.localtime(time.time()))))
# bonds
if len(btypes):
fileobj.write('\n# bonds\n')
fileobj.write('bond_style harmonic\n')
for ib, btype in enumerate(btypes):
fileobj.write('bond_coeff %6d' % (ib + 1))
for value in self.bonds.nvh[btype]:
fileobj.write(' ' + str(value))
fileobj.write(' # ' + btype + '\n')
# angles
if len(atypes):
fileobj.write('\n# angles\n')
fileobj.write('angle_style harmonic\n')
for ia, atype in enumerate(atypes):
fileobj.write('angle_coeff %6d' % (ia + 1))
for value in self.angles.nvh[atype]:
fileobj.write(' ' + str(value))
fileobj.write(' # ' + atype + '\n')
# dihedrals
if len(dtypes):
fileobj.write('\n# dihedrals\n')
fileobj.write('dihedral_style opls\n')
for i, dtype in enumerate(dtypes):
fileobj.write('dihedral_coeff %6d' % (i + 1))
for value in self.dihedrals.nvh[dtype]:
fileobj.write(' ' + str(value))
fileobj.write(' # ' + dtype + '\n')
# Lennard Jones settings
fileobj.write('\n# L-J parameters\n')
fileobj.write('pair_style lj/cut/coul/long 10.0 7.4' +
' # consider changing these parameters\n')
fileobj.write('special_bonds lj/coul 0.0 0.0 0.5\n')
data = self.data['one']
for ia, atype in enumerate(atoms.types):
if len(atype) < 2:
atype = atype + ' '
fileobj.write('pair_coeff ' + str(ia + 1) + ' ' + str(ia + 1))
for value in data[atype][:2]:
fileobj.write(' ' + str(value))
fileobj.write(' # ' + atype + '\n')
fileobj.write('pair_modify shift yes mix geometric\n')
# Charges
fileobj.write('\n# charges\n')
for ia, atype in enumerate(atoms.types):
if len(atype) < 2:
atype = atype + ' '
fileobj.write('set type ' + str(ia + 1))
fileobj.write(' charge ' + str(data[atype][2]))
fileobj.write(' # ' + atype + '\n')
def get_bond_matrix(sbu):
"""Guesses the bond order in neighbourlist based on covalent radii
the radii for BO > 1 are extrapolated by removing 0.1 Angstroms by order
see Beatriz Cordero, Veronica Gomez, Ana E. Platero-Prats, Marc Reves, Jorge Echeverria,
Eduard Cremades, Flavia Barragan and Santiago Alvarez (2008).
"Covalent radii revisited".
Dalton Trans. (21): 2832-2838
http://dx.doi.org/10.1039/b801115j
"""
# first guess
bonds = numpy.zeros((len(sbu), len(sbu)))
symbols = numpy.array(sbu.get_chemical_symbols())
numbers = numpy.array(sbu.get_atomic_numbers())
positions = numpy.array(sbu.get_positions())
BO1 = numpy.array([covalent_radii[n] if n > 0 else 0.35 for n in numbers])
BO2 = BO1 - 0.15
BO3 = BO2 - 0.15
nl1 = NeighborList(cutoffs=BO1,
bothways=True,
self_interaction=False,
skin=0.1)
nl2 = NeighborList(cutoffs=BO2,
bothways=True,
self_interaction=False,
skin=0.1)
nl3 = NeighborList(cutoffs=BO3,
bothways=True,
self_interaction=False,
skin=0.1)
nl1.update(sbu)
nl2.update(sbu)
nl3.update(sbu)
for atom in sbu:
i1, _ = nl1.get_neighbors(atom.index)
i2, _ = nl2.get_neighbors(atom.index)
i3, _ = nl3.get_neighbors(atom.index)
bonds[atom.index, i1] = 1.0
bonds[atom.index, i2] = 2.0
bonds[atom.index, i3] = 3.0
# cleanup with particular cases
# identify particular atoms
hydrogens = numpy.where(symbols == "H")[0]
metals = numpy.where(is_metal(symbols))[0]
alkali = numpy.where(is_alkali(symbols))[0]
# the rest is dubbed "organic"
organic = numpy.ones(bonds.shape)
organic[hydrogens, :] = False
organic[metals, :] = False
organic[alkali, :] = False
organic[:, hydrogens] = False
organic[:, metals] = False
organic[:, alkali] = False
organic = numpy.where(organic)[0]
# Hydrogen has BO of 1
bonds_h = bonds[hydrogens]
bonds_h[bonds_h > 1.0] = 1.0
bonds[hydrogens, :] = bonds_h
bonds[:, hydrogens] = bonds_h.T
#Metal-Metal bonds: if no special case, nominal bond
ix = numpy.ix_(metals, metals)
bix = bonds[ix]
bix[numpy.nonzero(bix)] = 0.25
bonds[ix] = bix
# no H-Metal bonds
ix = numpy.ix_(metals, hydrogens)
bonds[ix] = 0.0
ix = numpy.ix_(hydrogens, metals)
bonds[ix] = 0.0
# no alkali-alkali bonds
ix = numpy.ix_(alkali, alkali)
bonds[ix] = 0.0
# no alkali-metal bonds
ix = numpy.ix_(metals, alkali)
bonds[ix] = 0.0
ix = numpy.ix_(alkali, metals)
bonds[ix] = 0.0
# metal-organic is coordination bond
ix = numpy.ix_(metals, organic)
bix = bonds[ix]
bix[numpy.nonzero(bix)] = 0.5
bonds[ix] = bix
ix = numpy.ix_(organic, metals)
bix = bonds[ix]
bix[numpy.nonzero(bix)] = 0.5
bonds[ix] = bix
# aromaticity and rings
rings = []
# first, use the compressed sparse graph object
# we only care about organic bonds and not hydrogens
graph_bonds = numpy.array(bonds > 0.99, dtype=float)
graph_bonds[hydrogens, :] = 0.0
graph_bonds[:, hydrogens] = 0.0
graph = csgraph.csgraph_from_dense(graph_bonds)
for sg in graph.indices:
subgraph = graph[sg]
for i, j in combinations(subgraph.indices, 2):
t0 = csgraph.breadth_first_tree(graph, i_start=i, directed=False)
t1 = csgraph.breadth_first_tree(graph, i_start=j, directed=False)
t0i = t0.indices
t1i = t1.indices
ring = sorted(set(list(t0i) + list(t1i) + [i, j, sg]))
# some conditions
seen = (ring in rings)
isring = (sorted(t0i[1:]) == sorted(t1i[1:]))
bigenough = (len(ring) >= 5)
smallenough = (len(ring) <= 10)
if isring and not seen and bigenough and smallenough:
rings.append(ring)
# we now have a list of all the shortest rings within
# the molecular graph. If planar, the ring might be aromatic
aromatic_epsilon = 0.1
aromatic = []
for ring in rings:
homocycle = (symbols[ring] == "C").all()
heterocycle = numpy.in1d(symbols[ring],
numpy.array(["C", "S", "N", "O"])).all()
if (homocycle and (len(ring) % 2) == 0) or heterocycle:
ring_positions = positions[ring]
# small function for coplanarity
coplanar = all([
numpy.linalg.det(numpy.array(x[:3]) - x[3]) < aromatic_epsilon
for x in combinations(ring_positions, 4)
])
if coplanar:
aromatic.append(ring)
# aromatic bond fixing
aromatic = numpy.array(aromatic).ravel()
ix = numpy.ix_(aromatic, aromatic)
bix = bonds[ix]
bix[numpy.nonzero(bix)] = 1.5
bonds[ix] = bix
# hydrogen bonds
# TODO
return bonds
def do_one_vacancy(bulk_supercell,
calculator,
relax_radial=0.0,
relax_symm_break=0.0,
nn_cutoff=0.0,
tol=1.0e-2):
bulk_supercell_pe = bulk_supercell.get_potential_energy()
vac_i = 0
# do unrelaxed (without perturbations)
vac = bulk_supercell.copy()
del vac[vac_i]
label = "ind_%d_Z_%d" % (vac_i, bulk_supercell.get_atomic_numbers()[vac_i])
unrelaxed_filename = "-%s-unrelaxed.xyz" % label
ase.io.write(os.path.join("..", unrelaxed_filename), vac, format='extxyz')
#evaluate(vac)
vac.set_calculator(calculator)
unrelaxed_vac_pe = vac.get_potential_energy()
# recreate with perturbations for relaxation
vac = bulk_supercell.copy()
if relax_radial != 0.0 or relax_symm_break != 0.0:
nl = NeighborList([nn_cutoff / 2.0] * len(bulk_supercell),
self_interaction=False,
bothways=True)
nl.update(bulk_supercell)
indices, offsets = nl.get_neighbors(vac_i)
offset_factor = relax_radial
for i, offset in zip(indices, offsets):
ri = vac.positions[vac_i] - (vac.positions[i] +
np.dot(offset, vac.get_cell()))
vac.positions[i] += offset_factor * ri
offset_factor += relax_symm_break
del vac[vac_i]
vac_pos = vac.positions[vac_i]
vac = relax_config(vac,
calculator,
relax_pos=True,
relax_cell=False,
tol=tol,
traj_file=None,
config_label=label,
from_base_model=True,
save_config=True)
relaxed_filename = "-%s-relaxed.xyz" % label
ase.io.write(os.path.join("..", relaxed_filename), vac, format='extxyz')
# already has calculator from relax_configs
vac_pe = vac.get_potential_energy()
if len(set(bulk_supercell.get_atomic_numbers())) == 1:
Ebulk = float(len(vac)) / float(
len(bulk_supercell)) * bulk_supercell_pe
else:
Ebulk = bulk_supercell_pe
Ef0 = unrelaxed_vac_pe - Ebulk
Ef = vac_pe - Ebulk
print("got vacancy", label, "cell energy", vac_pe, "n_atoms", len(vac))
print("got bulk energy", Ebulk, " (scaled to (N-1)/N if single component)")
return (label, unrelaxed_filename, Ef0, relaxed_filename, Ef,
int(bulk_supercell.get_atomic_numbers()[vac_i]), vac_pos)
def build_neighbor_list(self):
'''
Builds a neighborlist for the calculation of bispectrum components for
a given ASE atoms object given in the calculate method.
'''
if self._backend == 'ase':
atoms = self._atoms
# cutoffs for each atom
cutoffs = [self.rcut / 2] * len(atoms)
# instantiate neighborlist calculator
nl = NeighborList(cutoffs, self_interaction=False, bothways=True, skin=0.0)
# provide atoms object to neighborlist calculator
nl.update(atoms)
# instantiate memory for neighbor separation vectors, periodic indices, and atomic numbers
center_atoms = np.zeros((len(atoms), 3), dtype=np.float64)
neighbors = []
neighbor_indices = []
atomic_numbers = []
max_len = 0
for i in range(len(atoms)):
# get center atom position
center_atom = atoms.positions[i]
center_atoms[i] = center_atom
# get indices and cell offsets of each neighbor
indices, offsets = nl.get_neighbors(i)
# add an empty list to neighbors and atomic numbers for population
neighbors.append([])
atomic_numbers.append([])
# the indices are already numpy arrays so just append as is
neighbor_indices.append(indices)
for j, offset in zip(indices, offsets):
# compute separation vector
pos = atoms.positions[j] + np.dot(offset, atoms.get_cell()) - center_atom
neighbors[i].append(pos)
atomic_numbers[i].append(atoms[j].number)
if len(neighbors[i]) > max_len:
max_len = len(neighbors[i])
# declare arrays to store the separation vectors, neighbor indices
# atomic numbers of each neighbor, and the atomic numbers of each
# site
neighborlist = np.zeros((len(atoms), max_len, 3), dtype=np.float64)
neighbor_inds = np.zeros((len(atoms), max_len), dtype=np.int64)
atm_nums = np.zeros((len(atoms), max_len), dtype=np.int64)
site_atomic_numbers = np.array(list(atoms.numbers), dtype=np.int64)
# populate the arrays with list elements
for i in range(len(atoms)):
neighborlist[i, :len(neighbors[i]), :] = neighbors[i]
neighbor_inds[i, :len(neighbors[i])] = neighbor_indices[i]
atm_nums[i, :len(neighbors[i])] = atomic_numbers[i]
elif self._backend == 'pymatgen':
from pymatgen.io.ase import AseAtomsAdaptor
struc = AseAtomsAdaptor.get_structure(self._atoms)
neighbors = struc.get_all_neighbors(self._rcut, include_index=True)
max_len = 0
for i, neighlist in enumerate(neighbors):
if len(neighlist) > max_len:
max_len = len(neighlist)
center_atoms = np.zeros((len(struc), 3), dtype=np.float64)
neighborlist = np.zeros((len(struc), max_len, 3), dtype=np.float64)
neighbor_inds = np.zeros((len(struc), max_len), dtype=np.int64)
atm_nums = np.zeros((len(struc), max_len), dtype=np.int64)
site_atomic_numbers = np.zeros(len(struc), dtype=np.int64)
for i, site in enumerate(struc):
neighlist = neighbors[i]
site_atomic_numbers[i] = site.specie.number
center_atoms[i] = site.coords
for j, neighbor in enumerate(neighlist):
neighborlist[i, j, :] = neighbor[0].coords - site.coords
neighbor_inds[i, j] = neighbor[2]
atm_nums[i, j] = neighbor[0].specie.number
else:
raise NotImplementedError('Specified backend not supported')
# assign these arrays to attributes
self.center_atoms = center_atoms
self.neighborlist = neighborlist
self.neighbor_indices = neighbor_inds
self.atomic_numbers = atm_nums
self.site_atomic_numbers = site_atomic_numbers
return
def update_neighbor_list(self, atoms):
cut = 0.5 * max(self.data['cutoffs'].values())
self.nl = NeighborList([cut] * len(atoms), skin=0,
bothways=True, self_interaction=False)
self.nl.update(atoms)
self.atoms = atoms
from ase.io import read, write
from ase.neighborlist import NeighborList
from ase.neighborlist import natural_cutoffs
nt = [0]*32
atoms = read('run-01.pdb')
nl = NeighborList(natural_cutoffs(atoms, 1.35))
nl.update(atoms)
o = open('nl.dat', 'w')
for i in range(len(atoms)):
indices, offsets = nl.get_neighbors(i)
nt[len(indices)] += 1
o.write('%d\n'%len(indices))
def get_all_interstitials(ats, unique_atoms):
"""Function to return list of all interstitial sites using Voronoi.py
Args:
ats(:ase:class:`Atoms`):Atoms object of structure.
positions(numpy array): Lattice sites to compute interstitials for.
Returns:
list of list, with inner list containing ['Interstitial Type', [x,y,z]]
Interstitial type can be of type 'B', 'C', 'N' corresponding to;
'B' Voronoi vertices.
'C' face centers.
'N' Edge centers.
"""
ints_list = []
#generate neighbours list.
for site_num in unique_atoms:
nl = NeighborList([2.0] * len(ats),
bothways=False,
self_interaction=True)
nl.update(ats)
site = np.array([
ats[site_num].position[0], ats[site_num].position[1],
ats[site_num].position[2]
])
points = []
indices, offsets = nl.get_neighbors(site_num)
print 'site_num:', site_num
for i, offset in zip(indices, offsets):
if offset[2] == 0.0:
print 'neighb:', i, ats.positions[i], offset, np.dot(
offset, ats.get_cell())
points.append(ats.positions[i] +
np.dot(offset, ats.get_cell()))
### converting list to numpy array
print "neighbors", len(points)
points = np.asarray(points)
voronoi = Voronoi()
### using tess object cntr to compute voronoi
cntr = voronoi.compute_voronoi(points)
### Voronoi vertices
### the first position in points is the site, therefore '0'
v = voronoi.get_vertices(0, cntr)
for i in range(len(v)):
ints_list.append(['B', v[i].tolist()])
### Voronoi face centers
f = voronoi.get_facecentroid(0, cntr)
for j in range(len(f)):
ints_list.append(['C', f[j].tolist()])
### Voronoi edge centers
e = voronoi.get_edgecenter(0, cntr)
for k in range(len(e)):
ints_list.append(['N', e[k].tolist()])
### return list of list ['Atom type', [x,y,z]]
return ints_list
def CoreShellFCC(atoms, type_a, type_b, ratio, a_cell, n_depth=-1):
r"""This routine generates cluster with ideal core-shell architecture,
so that atoms of type_a are placed on the surface
and atoms of type_b are forming the core of nanoparticle.
The 'surface' of nanoparticle is defined as atoms
with unfinished coordination shell.
Parameters
----------
atoms: ase.Atoms
ase Atoms object, containing atomic cluster.
type_a: string
Symbol of chemical element to be placed on the shell.
type_b: string
Symbol of chemical element to be placed in the core.
ratio: float
Guards the number of shell atoms, type_a:type_b = ratio:(1-ratio)
a_cell: float
Parameter of FCC cell, in Angstrom.
Required for calculation of neighbor distances in for infinite
crystal.
n_depth: int
Number of layers of the shell formed by atoms ratio.
Default value -1 is ignored and n_depth is calculated according
ratio. If n_depth is set then value of ratio is ignored.
Returns
-------
Function returns ASE atoms object which
contains bimetallic core-shell cluster
Notes
-----
The criterion of the atom beeing on the surface is incompletnes
of it's coordination shell. For the most outer atoms the first
coordination shell will be incomplete (coordination number
is less then 12 for FCC), for the second layer --
second coordination shell( CN1 + CN2 < 12 + 6) and so on.
In this algorithm each layer is tagged by the number
('depth'), take care if used with other routines
dealing with tags (add_adsorbate etc).
First, atoms with unfinished first shell are replaced
by atoms type_a, then second, and so on.
The last depth surface layer is replaced by random
to maintain given ratio value.
Example
--------
>>> atoms = FaceCenteredCubic('Ag',
[(1, 0, 0), (1, 1, 0), (1, 1, 1)], [7,8,7], 4.09)
>>> atoms = CoreShellFCC(atoms, 'Pt', 'Ag', 0.6, 4.09)
>>> view(atoms)
"""
# 0 < ratio < 1
target_x = ratio
if n_depth != -1:
target_x = 1 # needed to label all needed layeres
def fill_by_tag(atoms, chems, tag):
"""Replaces all atoms within selected layer"""
for i in xrange(0, len(atoms)):
if atoms[i].tag == tag:
chems[i] = type_a
return
# coord numbers for FCC:
coord_nums = [1, 12, 6, 24, 12, 24, 8, 48, 6, 36, 24, 24, 24, 72, 48,
12, 48, 30, 72, 24]
# coordination radii obtained from this array as R = sqrt(coord_radii)*a/2
coord_radii = [0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 30,
32, 34, 36, 38, 40]
## generate FCC cluster ##
#atoms = FaceCenteredCubic(type_b, surfaces, layers, a_cell)
n_atoms = len(atoms)
## tag layers ##
positions = [0] # number of positions in layer
n_tag = 0 # number of tags to check if there is enought layers
n_shell = 0 # depth of the shell
while (n_tag < n_atoms * target_x):
n_shell += 1
if (n_depth != -1)and(n_shell > n_depth):
break
neiblist = NeighborList(
[
a_cell / 2.0 * sqrt(coord_radii[n_shell]) / 2.0 + 0.0001
] * n_atoms,
self_interaction=False, bothways=True
)
neiblist.build(atoms)
for i in xrange(0, n_atoms):
indeces, offsets = neiblist.get_neighbors(i)
if (atoms[i].tag == 0):
if (len(indeces) < sum(coord_nums[1:n_shell + 1])):
# coord shell is not full -> atom is on surface!
atoms[i].tag = n_shell
n_tag += 1
# save the count of positions at each layer:
positions.append(n_tag - sum(positions[0:n_shell]))
## populate layers ##
chems = atoms.get_chemical_symbols()
n_type_a = 0 # number of changes B -> A
if (n_tag < n_atoms * target_x)and(n_depth == -1):
# raise exception?
return None
else:
n_filled = n_shell - 1 # number of totally filled layers
ilayer = 1
while (ilayer < n_filled + 1):
fill_by_tag(atoms, chems, ilayer)
n_type_a += positions[ilayer]
ilayer += 1
while (n_type_a < n_atoms * target_x)and(n_depth == -1):
i = random.randint(0, n_atoms - 1)
if (atoms[i].tag == n_shell):
if (chems[i] == type_b):
chems[i] = type_a
n_type_a += 1
atoms.set_chemical_symbols(chems)
## check number of atoms ##
checkn_a = 0
for element in chems:
if element == type_a:
checkn_a += 1
assert n_type_a == checkn_a
return atoms
class RepulsivePotential(Calculator):
""" ASE Calculator representing the repulsive potentials in a DFTB
parameter set. Arguments:
atoms: an ASE atoms object to which the calculator will be attached
skfdict: dict with the (paths to the) SKF files containing the
(exponential+spline-based) repulsive potentials, one
for every (alphabetically sorted) element pair, e.g.:
{'O-O':'O-O.skf', 'H-O':'H-O.skf', 'H-H':'H-H.skf'}.
If equal to None, all files are assumed to reside in
the $DFTB_PREFIX folder and formatted as *-*.skf
as in the example above.
"""
implemented_properties = ['energy', 'forces']
def __init__(self, atoms, skfdict=None):
Calculator.__init__(self)
elements = np.unique(atoms.get_chemical_symbols())
self.pairs = get_skf_prefixes(elements, redundant=False)
rcut = 0.
self.func = {}
for p in self.pairs:
if skfdict is None:
f = os.environ['DFTB_PREFIX'] + '/%s.skf' % p
else:
assert p in skfdict, 'No SKF file specified for %s' % p
f = skfdict[p]
assert os.path.exists(f), 'SKF file %s does not exist' % f
self.func[p] = read_spline_from_skf(f)
rcut = max([rcut, self.func[p].rcut])
self.nl = NeighborList([rcut * Bohr / 2.] * len(atoms),
skin=1.,
bothways=False,
self_interaction=False)
def calculate(self, atoms, properties, system_changes):
Calculator.calculate(self, atoms, properties, system_changes)
N = len(atoms)
energy, forces = 0, np.zeros((N, 3))
cell = atoms.get_cell()
sym = atoms.get_chemical_symbols()
pos = atoms.get_positions()
self.nl.update(atoms)
for i in range(N):
indices, offsets = self.nl.get_neighbors(i)
p = pos[indices] + np.dot(offsets, cell)
r = cdist(p, [pos[i]])
v = pos[i] - p
for j, index in enumerate(indices):
p = '-'.join(sorted([sym[i], sym[index]]))
d = r[j][0]
energy += self.func[p](d, der=0)
f = self.func[p](d, der=1) * v[j] / d
forces[index] += f
forces[i] -= f
self.results = {'energy': energy, 'forces': forces}
def get_neighbours(atoms, r_cut, self_interaction=False):
"""Return a list of pairs of atoms within a given distance of each other.
If matscipy can be imported, then this will directly call matscipy's
neighbourlist function. Otherwise it will use ASE's NeighborList object.
Args:
atoms: ase.atoms object to calculate neighbours for
r_cut: cutoff radius (float). Pairs of atoms are considered neighbours
if they are within a distance r_cut of each other (note that this
is double the parameter used in the ASE's neighborlist module)
Returns: a tuple (i_list, j_list, d_list, fixed_atoms):
i_list, j_list: i and j indices of each neighbour pair
d_list: absolute distance between the corresponding pair
fixed_atoms: indices of any fixed atoms
"""
if isinstance(atoms, Filter):
atoms = atoms.atoms
if have_matscipy:
i_list, j_list, d_list = neighbour_list('ijd', atoms, r_cut)
else:
radii = [r_cut / 2 for i in range(len(atoms))]
nl = NeighborList(radii,
sorted=False,
self_interaction=False,
bothways=True)
nl.update(atoms)
i_list = []
j_list = []
d_list = []
for i, atom in enumerate(atoms):
posn_i = atom.position
indices, offsets = nl.get_neighbors(i)
assert len(indices) == len(offsets)
for j, offset in zip(indices, offsets):
# Offsets represent how far away an atom is from its pair in terms
# of the repeating cell - for instance, an atom i might be in cell
# (0, 0, 0) while the neighbouring atom j is in cell (0, 1, 1). To
# get the true position we have to correct for the offset:
posn_j = atoms.positions[j] + np.dot(offset, atoms.get_cell())
distance = np.sqrt(((posn_j - posn_i)**2).sum())
i_list.append(i)
j_list.append(j)
d_list.append(distance)
i_list = np.array(i_list)
j_list = np.array(j_list)
d_list = np.array(d_list)
# filter out self-interactions (across PBC)
if not self_interaction:
mask = i_list != j_list
i_list = i_list[mask]
j_list = j_list[mask]
d_list = d_list[mask]
# filter out bonds where 1st atom (i) in pair is fixed
fixed_atoms = []
for constraint in atoms.constraints:
if isinstance(constraint, FixAtoms):
fixed_atoms.extend(list(constraint.index))
else:
raise TypeError(
'only FixAtoms constraints are supported by Precon class')
return i_list, j_list, d_list, fixed_atoms
