def __init__(self, rc=7.0, width=1.0):
""" TIP4P potential for water.
http://dx.doi.org/10.1063/1.445869
Requires an atoms object of OHH,OHH, ... sequence
Correct TIP4P charges and LJ parameters set automatically.
Virtual interaction sites implemented in the following scheme:
Original atoms object has no virtual sites.
When energy/forces are requested:
* virtual sites added to temporary xatoms object
* energy / forces calculated
* forces redistributed from virtual sites to actual atoms object
This means you do not get into trouble when propagating your system
with MD while having to skip / account for massless virtual sites.
This also means that if using for QM/MM MD with GPAW, the EmbedTIP4P
class must be used.
"""
TIP3P.__init__(self, rc, width)
self.energy = None
self.forces = None
def test_combine_mm2():
# More biased initial positions for faster test. Set
# to false for a slower, harder test.
fast_test = True
atoms = make_4mer()
atoms.constraints = FixBondLengths([(3 * i + j, 3 * i + (j + 1) % 3)
for i in range(int(len(atoms) // 3))
for j in [0, 1, 2]])
atoms.calc = TIP3P(np.Inf)
tag = '4mer_tip3_opt.'
opt = FIRE(atoms, logfile=tag + 'log', trajectory=tag + 'traj')
opt.run(fmax=0.05)
tip3_pos = atoms.get_positions()
sig = np.array([sigma0, 0, 0])
eps = np.array([epsilon0, 0, 0])
rc = np.Inf
idxes = [[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10, 11],
list(range(6)),
list(range(9)),
list(range(6, 12))]
for ii, idx in enumerate(idxes):
atoms = make_4mer()
if fast_test:
atoms.set_positions(tip3_pos)
atoms.constraints = FixBondLengths([(3 * i + j, 3 * i + (j + 1) % 3)
for i in range(len(atoms) // 3)
for j in [0, 1, 2]])
atoms.calc = CombineMM(idx,
3,
3,
TIP3P(rc),
TIP3P(rc),
sig,
eps,
sig,
eps,
rc=rc)
tag = '4mer_combtip3_opt_{0:02d}.'.format(ii)
opt = FIRE(atoms, logfile=tag + 'log', trajectory=tag + 'traj')
opt.run(fmax=0.05)
assert ((abs(atoms.positions - tip3_pos) < 1e-8).all())
print('{0}: {1!s:>28s}: Same Geometry as TIP3P'.format(
atoms.calc.name, idx))
def make_dimer(constraint=True):
"""Prepare atoms object for testing"""
dimer = s22.create_s22_system("Water_dimer")
calc = TIP3P(rc=9.0)
dimer.calc = calc
if constraint:
dimer.constraints = FixBondLengths([(3 * i + j, 3 * i + (j + 1) % 3)
for i in range(2)
for j in [0, 1, 2]])
return dimer
def test_water_dimer(internal, order):
internal = True
order = 0
rng = np.random.RandomState(1)
atoms = atoms_ref.copy()
atoms.calc = TIP3P()
atoms.rattle(0.01, rng=rng)
nwater = len(atoms) // 3
cons = Constraints(atoms)
for i in range(nwater):
cons.fix_bond((3 * i, 3 * i + 1), target=rOH)
cons.fix_bond((3 * i, 3 * i + 2), target=rOH)
cons.fix_angle((3 * i + 1, 3 * i, 3 * i + 2), target=angleHOH)
# Remove net translation and rotation
try:
cons.fix_translation()
except DuplicateConstraintError:
pass
try:
cons.fix_rotation()
except DuplicateConstraintError:
pass
sella_kwargs = dict(
order=order,
trajectory='test.traj',
eta=1e-6,
delta0=1e-2,
)
if internal:
sella_kwargs['internal'] = Internals(atoms,
cons=cons,
allow_fragments=True)
else:
sella_kwargs['constraints'] = cons
opt = Sella(atoms, **sella_kwargs)
opt.delta = 0.05
opt.run(fmax=1e-3)
print("First run done")
atoms.rattle()
opt.run(fmax=1e-3)
Ufree = opt.pes.get_Ufree()
g = opt.pes.get_g() @ Ufree
np.testing.assert_allclose(g, 0, atol=1e-3)
opt.pes.diag(gamma=1e-16)
H = opt.pes.get_HL().project(Ufree)
assert np.sum(H.evals < 0) == order, H.evals
def test_rattle():
i = LJInteractions({('O', 'O'): (epsilon0, sigma0)})
for calc in [
TIP3P(),
SimpleQMMM([0, 1, 2], TIP3P(), TIP3P(), TIP3P()),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), i)
]:
dimer = s22('Water_dimer')
for m in [0, 3]:
dimer.set_angle(m + 1, m, m + 2, angleHOH)
dimer.set_distance(m, m + 1, rOH, fix=0)
dimer.set_distance(m, m + 2, rOH, fix=0)
fixOH1 = [(3 * i, 3 * i + 1) for i in range(2)]
fixOH2 = [(3 * i, 3 * i + 2) for i in range(2)]
fixHH = [(3 * i + 1, 3 * i + 2) for i in range(2)]
dimer.set_constraint(FixBondLengths(fixOH1 + fixOH2 + fixHH))
dimer.calc = calc
e = dimer.get_potential_energy()
md = VelocityVerlet(dimer,
8.0 * units.fs,
trajectory=calc.name + '.traj',
logfile=calc.name + '.log',
loginterval=5)
md.run(25)
de = dimer.get_potential_energy() - e
assert abs(de - -0.028) < 0.001
def test_turbomole_qmmm():
"""Test the Turbomole calculator in simple QMMM and
explicit interaction QMMM simulations."""
r = rOH
a = angleHOH * pi / 180
D = np.linspace(2.5, 3.5, 30)
interaction = LJInteractions({('O', 'O'): (epsilon0, sigma0)})
qm_par = {'esp fit': 'kollman', 'multiplicity': 1}
for calc in [
TIP3P(),
SimpleQMMM([0, 1, 2], Turbomole(**qm_par), TIP3P(), TIP3P()),
SimpleQMMM([0, 1, 2],
Turbomole(**qm_par),
TIP3P(),
TIP3P(),
vacuum=3.0),
EIQMMM([0, 1, 2], Turbomole(**qm_par), TIP3P(), interaction),
EIQMMM([3, 4, 5],
Turbomole(**qm_par),
TIP3P(),
interaction,
vacuum=3.0),
EIQMMM([0, 1, 2],
Turbomole(**qm_par),
TIP3P(),
interaction,
vacuum=3.0)
]:
dimer = Atoms('H2OH2O',
[(r * cos(a), 0, r * sin(a)), (r, 0, 0), (0, 0, 0),
(r * cos(a / 2), r * sin(a / 2), 0),
(r * cos(a / 2), -r * sin(a / 2), 0), (0, 0, 0)])
dimer.calc = calc
E = []
F = []
for d in D:
dimer.positions[3:, 0] += d - dimer.positions[5, 0]
E.append(dimer.get_potential_energy())
F.append(dimer.get_forces())
F = np.array(F)
F1 = np.polyval(np.polyder(np.polyfit(D, E, 7)), D)
F2 = F[:, :3, 0].sum(1)
error = abs(F1 - F2).max()
assert error < 0.9
dimer.set_constraint(
FixInternals(bonds=[(r, (0, 2)), (r, (1, 2)), (r, (3, 5)),
(r, (4, 5))],
angles_deg=[(angleHOH, (0, 2, 1)),
(angleHOH, (3, 5, 4))]))
opt = BFGS(dimer,
trajectory=calc.name + '.traj',
logfile=calc.name + 'd.log')
opt.run(0.01)
e0 = dimer.get_potential_energy()
d0 = dimer.get_distance(2, 5)
R = dimer.positions
v1 = R[1] - R[5]
v2 = R[5] - (R[3] + R[4]) / 2
a0 = np.arccos(
np.dot(v1, v2) /
(np.dot(v1, v1) * np.dot(v2, v2))**0.5) / np.pi * 180
fmt = '{0:>20}: {1:.3f} {2:.3f} {3:.3f} {4:.1f}'
print(fmt.format(calc.name, -min(E), -e0, d0, a0))
from ase.md.langevin import Langevin
from ase.io import Trajectory
import ase.units as u
md_cls_and_kwargs = [
(VelocityVerlet, {}),
(Langevin, {
"temperature": 300 * u.kB,
"friction": 0.02
}),
]
# prepare atoms object for testing
dimer = s22.create_s22_system("Water_dimer")
calc = TIP3P(rc=9.0)
dimer.constraints = FixBondLengths([(3 * i + j, 3 * i + (j + 1) % 3)
for i in range(2) for j in [0, 1, 2]])
def fmax(forces):
return np.sqrt((forces**2).sum(axis=1).max())
def test_opt(cls, atoms, calc, logfile="opt.log", trajectory="opt.traj"):
"""run optimization and verify that log and trajectory coincide"""
# clean files to make sure the correct ones are tested
for file in (*Path().glob("*.log"), *Path().glob("*.traj")):
file.unlink()
atoms2 = make_atoms()
atoms2.translate([0., 3, 0])
atoms2.rotate(180, 'y')
atoms2.translate([3, 0, 0])
atoms += atoms2
return atoms
# More biased initial positions for faster test. Set
# to false for a slower, harder test.
fast_test = True
atoms = make_4mer()
atoms.constraints = FixBondLengths([(3 * i + j, 3 * i + (j + 1) % 3)
for i in range(int(len(atoms) // 3))
for j in [0, 1, 2]])
atoms.calc = TIP3P(np.Inf)
tag = '4mer_tip3_opt.'
opt = FIRE(atoms, logfile=tag+'log', trajectory=tag+'traj')
opt.run(fmax=0.05)
tip3_pos = atoms.get_positions()
sig = np.array([sigma0, 0, 0 ])
eps = np.array([epsilon0, 0, 0 ])
rc = np.Inf
idxes = [[0, 1, 2], [3, 4 ,5], [6, 7, 8], [9, 10, 11],
list(range(6)), list(range(9)), list(range(6, 12))]
for ii, idx in enumerate(idxes):
atoms = make_4mer()
if fast_test:
atoms.set_positions(tip3_pos)
def calc():
return TIP3P(rc=9.0)
import ase.units as units
from ase.calculators.tip3p import TIP3P, epsilon0, sigma0, rOH, angleHOH
from ase.calculators.qmmm import SimpleQMMM, EIQMMM, LJInteractions
from ase.data.s22 import create_s22_system as s22
from ase.md.verlet import VelocityVerlet
from ase.constraints import FixBondLengths
i = LJInteractions({('O', 'O'): (epsilon0, sigma0)})
for calc in [
TIP3P(),
SimpleQMMM([0, 1, 2], TIP3P(), TIP3P(), TIP3P()),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), i)
]:
dimer = s22('Water_dimer')
for m in [0, 3]:
dimer.set_angle(m + 1, m, m + 2, angleHOH)
dimer.set_distance(m, m + 1, rOH, fix=0)
dimer.set_distance(m, m + 2, rOH, fix=0)
fixOH1 = [(3 * i, 3 * i + 1) for i in range(2)]
fixOH2 = [(3 * i, 3 * i + 2) for i in range(2)]
fixHH = [(3 * i + 1, 3 * i + 2) for i in range(2)]
dimer.set_constraint(FixBondLengths(fixOH1 + fixOH2 + fixHH))
dimer.calc = calc
e = dimer.get_potential_energy()
md = VelocityVerlet(dimer,
2.0 * units.fs,
from __future__ import print_function
from ase.data import s22
from ase.calculators.tip3p import TIP3P, epsilon0, sigma0
from ase.calculators.qmmm import EIQMMM, LJInteractions, Embedding
from gpaw import GPAW
# Create system
atoms = s22.create_s22_system('Water_dimer')
atoms.center(vacuum=4.0)
# Make QM atoms selection of first water molecule:
qm_idx = range(3)
# Set up interaction & embedding object
interaction = LJInteractions({('O', 'O'): (epsilon0, sigma0)})
embedding = Embedding(rc=0.02) # Short range analytical potential cutoff
# Set up calculator
atoms.calc = EIQMMM(qm_idx,
GPAW(txt='qm.out'),
TIP3P(),
interaction,
embedding=embedding,
vacuum=None, # if None, QM cell = MM cell
output='qmmm.log')
print(atoms.get_potential_energy())
"""Test TIP3P forces."""
from math import cos, sin
from ase import Atoms
from ase.calculators.tip3p import TIP3P, rOH, thetaHOH, set_tip3p_charges
r = rOH
a = thetaHOH
dimer = Atoms('H2OH2O',
[(r * cos(a), 0, r * sin(a)),
(r, 0, 0),
(0, 0, 0),
(r * cos(a / 2), r * sin(a / 2), 0),
(r * cos(a / 2), -r * sin(a / 2), 0),
(0, 0, 0)])
set_tip3p_charges(dimer)
dimer.calc = TIP3P(rc=4.0, width=2.0) # put O-O distance in the cutoff range
dimer.positions[3:, 0] += 2.8
F = dimer.get_forces()
print(F)
dF = dimer.calc.calculate_numerical_forces(dimer) - F
print(dF)
assert abs(dF).max() < 2e-6
dexp = 2.74
aexp = 27
D = np.linspace(2.5, 3.5, 30)
i = LJInteractions({('O', 'O'): (epsilon0, sigma0)})
# General LJ interaction object
sigma_mm = np.array([0, 0, sigma0])
epsilon_mm = np.array([0, 0, epsilon0])
sigma_qm = np.array([0, 0, sigma0])
epsilon_qm = np.array([0, 0, epsilon0])
ig = LJInteractionsGeneral(sigma_qm, epsilon_qm, sigma_mm, epsilon_mm)
for calc in [
TIP3P(),
SimpleQMMM([0, 1, 2], TIP3P(), TIP3P(), TIP3P()),
SimpleQMMM([0, 1, 2], TIP3P(), TIP3P(), TIP3P(), vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), i),
EIQMMM([3, 4, 5], TIP3P(), TIP3P(), i, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), i, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), ig),
EIQMMM([3, 4, 5], TIP3P(), TIP3P(), ig, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), ig, vacuum=3.0)
]:
dimer = Atoms('H2OH2O', [(r * cos(a), 0, r * sin(a)), (r, 0, 0), (0, 0, 0),
(r * cos(a / 2), r * sin(a / 2), 0),
(r * cos(a / 2), -r * sin(a / 2), 0), (0, 0, 0)])
dimer.calc = calc
E = []
from ase import Atoms
from ase.calculators.tip3p import TIP3P, epsilon0, sigma0, rOH, angleHOH
from ase.calculators.qmmm import SimpleQMMM, EIQMMM, LJInteractions
from ase.calculators.turbomole import Turbomole
from ase.constraints import FixInternals
from ase.optimize import BFGS
r = rOH
a = angleHOH * pi / 180
D = np.linspace(2.5, 3.5, 30)
interaction = LJInteractions({('O', 'O'): (epsilon0, sigma0)})
qm_par = {'esp fit': 'kollman', 'multiplicity': 1}
for calc in [
TIP3P(),
SimpleQMMM([0, 1, 2], Turbomole(**qm_par), TIP3P(), TIP3P()),
SimpleQMMM([0, 1, 2],
Turbomole(**qm_par),
TIP3P(),
TIP3P(),
vacuum=3.0),
EIQMMM([0, 1, 2], Turbomole(**qm_par), TIP3P(), interaction),
EIQMMM([3, 4, 5],
Turbomole(**qm_par),
TIP3P(),
interaction,
vacuum=3.0),
EIQMMM([0, 1, 2],
Turbomole(**qm_par),
TIP3P(),
def test_qmmm():
from math import cos, sin, pi
import numpy as np
# import matplotlib.pyplot as plt
import ase.units as units
from ase import Atoms
from ase.calculators.tip3p import TIP3P, epsilon0, sigma0, rOH, angleHOH
from ase.calculators.qmmm import (SimpleQMMM, EIQMMM, LJInteractions,
LJInteractionsGeneral)
from ase.constraints import FixInternals
from ase.optimize import GPMin
r = rOH
a = angleHOH * pi / 180
# From https://doi.org/10.1063/1.445869
eexp = 6.50 * units.kcal / units.mol
dexp = 2.74
aexp = 27
D = np.linspace(2.5, 3.5, 30)
i = LJInteractions({('O', 'O'): (epsilon0, sigma0)})
# General LJ interaction object
sigma_mm = np.array([0, 0, sigma0])
epsilon_mm = np.array([0, 0, epsilon0])
sigma_qm = np.array([0, 0, sigma0])
epsilon_qm = np.array([0, 0, epsilon0])
ig = LJInteractionsGeneral(sigma_qm, epsilon_qm, sigma_mm, epsilon_mm, 3)
for calc in [
TIP3P(),
SimpleQMMM([0, 1, 2], TIP3P(), TIP3P(), TIP3P()),
SimpleQMMM([0, 1, 2], TIP3P(), TIP3P(), TIP3P(), vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), i),
EIQMMM([3, 4, 5], TIP3P(), TIP3P(), i, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), i, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), ig),
EIQMMM([3, 4, 5], TIP3P(), TIP3P(), ig, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), ig, vacuum=3.0)
]:
dimer = Atoms('H2OH2O',
[(r * cos(a), 0, r * sin(a)), (r, 0, 0), (0, 0, 0),
(r * cos(a / 2), r * sin(a / 2), 0),
(r * cos(a / 2), -r * sin(a / 2), 0), (0, 0, 0)])
dimer.calc = calc
E = []
F = []
for d in D:
dimer.positions[3:, 0] += d - dimer.positions[5, 0]
E.append(dimer.get_potential_energy())
F.append(dimer.get_forces())
F = np.array(F)
# plt.plot(D, E)
F1 = np.polyval(np.polyder(np.polyfit(D, E, 7)), D)
F2 = F[:, :3, 0].sum(1)
error = abs(F1 - F2).max()
assert error < 0.01
dimer.constraints = FixInternals(bonds=[(r, (0, 2)), (r, (1, 2)),
(r, (3, 5)), (r, (4, 5))],
angles=[(a, (0, 2, 1)),
(a, (3, 5, 4))])
opt = GPMin(dimer,
trajectory=calc.name + '.traj',
logfile=calc.name + 'd.log')
opt.run(0.01)
e0 = dimer.get_potential_energy()
d0 = dimer.get_distance(2, 5)
R = dimer.positions
v1 = R[1] - R[5]
v2 = R[5] - (R[3] + R[4]) / 2
a0 = np.arccos(
np.dot(v1, v2) /
(np.dot(v1, v1) * np.dot(v2, v2))**0.5) / np.pi * 180
fmt = '{0:>20}: {1:.3f} {2:.3f} {3:.3f} {4:.1f}'
print(fmt.format(calc.name, -min(E), -e0, d0, a0))
assert abs(e0 + eexp) < 0.002
assert abs(d0 - dexp) < 0.01
assert abs(a0 - aexp) < 4
print(fmt.format('reference', 9.999, eexp, dexp, aexp))
atoms2.translate([0., 3, 0])
atoms2.rotate(180, 'y')
atoms2.translate([3, 0, 0])
atoms += atoms2
return atoms
# More biased initial positions for faster test. Set
# to false for a slower, harder test.
fast_test = True
atoms = make_4mer()
atoms.constraints = FixBondLengths([(3 * i + j, 3 * i + (j + 1) % 3)
for i in range(int(len(atoms) // 3))
for j in [0, 1, 2]])
atoms.calc = TIP3P(np.Inf)
tag = '4mer_tip3_opt.'
opt = FIRE(atoms, logfile=tag + 'log', trajectory=tag + 'traj')
opt.run(fmax=0.05)
tip3_pos = atoms.get_positions()
sig = np.array([sigma0, 0, 0])
eps = np.array([epsilon0, 0, 0])
rc = np.Inf
idxes = [[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10, 11],
list(range(6)),
list(range(9)),
list(range(6, 12))]
for ii, idx in enumerate(idxes):
atoms = make_4mer()
eexp = 6.50 * units.kcal / units.mol
dexp = 2.74
aexp = 27
D = np.linspace(2.5, 3.5, 30)
i = LJInteractions({('O', 'O'): (epsilon0, sigma0)})
# General LJ interaction object
sigma_mm = np.array([0, 0, sigma0])
epsilon_mm = np.array([0, 0, epsilon0])
sigma_qm = np.array([0, 0, sigma0])
epsilon_qm = np.array([0, 0, epsilon0])
ig = LJInteractionsGeneral(sigma_qm, epsilon_qm, sigma_mm, epsilon_mm, 3)
for calc in [TIP3P(),
SimpleQMMM([0, 1, 2], TIP3P(), TIP3P(), TIP3P()),
SimpleQMMM([0, 1, 2], TIP3P(), TIP3P(), TIP3P(), vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), i),
EIQMMM([3, 4, 5], TIP3P(), TIP3P(), i, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), i, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), ig),
EIQMMM([3, 4, 5], TIP3P(), TIP3P(), ig, vacuum=3.0),
EIQMMM([0, 1, 2], TIP3P(), TIP3P(), ig, vacuum=3.0)]:
dimer = Atoms('H2OH2O',
[(r * cos(a), 0, r * sin(a)),
(r, 0, 0),
(0, 0, 0),
(r * cos(a / 2), r * sin(a / 2), 0),
(r * cos(a / 2), -r * sin(a / 2), 0),
(0, 0, 0)])
def test_combine_mm():
"""Test CombineMM forces by combining tip3p and tip4p with them selves, and
by combining tip3p with tip4p and testing against numerical forces.
Also test LJInterationsGeneral with CombineMM """
from math import cos, sin, pi
import numpy as np
from ase import Atoms
from ase import units
from ase.calculators.counterions import AtomicCounterIon as ACI
from ase.calculators.combine_mm import CombineMM
from ase.calculators.qmmm import LJInteractionsGeneral
from ase.calculators.tip3p import TIP3P, rOH, angleHOH
from ase.calculators.tip4p import TIP4P
from ase.calculators.tip3p import epsilon0 as eps3
from ase.calculators.tip3p import sigma0 as sig3
from ase.calculators.tip4p import epsilon0 as eps4
from ase.calculators.tip4p import sigma0 as sig4
def make_atoms():
r = rOH
a = angleHOH * pi / 180
dimer = Atoms('H2OH2O',
[(r * cos(a), 0, r * sin(a)), (r, 0, 0), (0, 0, 0),
(r * cos(a / 2), r * sin(a / 2), 0),
(r * cos(a / 2), -r * sin(a / 2), 0), (0, 0, 0)])
dimer = dimer[[2, 0, 1, 5, 3, 4]]
# put O-O distance in the cutoff range
dimer.positions[3:, 0] += 2.8
return dimer
dimer = make_atoms()
rc = 3.0
for (TIPnP, (eps, sig), nm) in zip([TIP3P, TIP4P],
((eps3, sig3), (eps4, sig4)), [3, 3]):
dimer.calc = TIPnP(rc=rc, width=1.0)
F1 = dimer.get_forces()
sigma = np.array([sig, 0, 0])
epsilon = np.array([eps, 0, 0])
dimer.calc = CombineMM([0, 1, 2],
nm,
nm,
TIPnP(rc=rc, width=1.0),
TIPnP(rc=rc, width=1.0),
sigma,
epsilon,
sigma,
epsilon,
rc=rc,
width=1.0)
F2 = dimer.get_forces()
dF = F1 - F2
print(TIPnP)
print(dF)
assert abs(dF).max() < 1e-8
# Also check a TIP3P/TIP4P combination against numerical forces:
eps1 = np.array([eps3, 0, 0])
sig1 = np.array([sig3, 0, 0])
eps2 = np.array([eps4, 0, 0])
sig2 = np.array([sig4, 0, 0])
dimer.calc = CombineMM([0, 1, 2], 3, 3, TIP3P(rc, 1.0), TIP4P(rc, 1.0),
sig1, eps1, sig2, eps2, rc, 1.0)
F2 = dimer.get_forces()
Fn = dimer.calc.calculate_numerical_forces(dimer, 1e-7)
dF = F2 - Fn
print('TIP3P/TIP4P')
print(dF)
assert abs(dF).max() < 1e-8
# LJInteractionsGeneral with CombineMM.
# As it is used within EIQMMM, but avoiding long calculations for tests.
# Total system is a unit test system comprised of:
# 2 Na ions playing the role of a 'QM' subsystem
# 2 Na ions as the 'Counterions'
# 2 Water molecules
dimer.calc = []
faux_qm = Atoms('2Na', positions=np.array([[1.4, -4, 0], [1.4, 4, 0]]))
ions = Atoms('2Na', positions=np.array([[1.4, 0, -4], [1.4, 0, 4]]))
mmatoms = ions + dimer
sigNa = 1.868 * (1.0 / 2.0)**(1.0 / 6.0) * 10
epsNa = 0.00277 * units.kcal / units.mol
# ACI for atoms 0 and 1 of the MM subsystem (2 and 3 for the total system)
# 1 atom 'per molecule'. The rest is TIP4P, 3 atoms per molecule:
calc = CombineMM(
[0, 1],
1,
3,
ACI(1, epsNa, sigNa), # calc 1
TIP4P(), # calc 2
[sigNa],
[epsNa], # LJs for subsystem 1
sig2,
eps2, # arrays for TIP4P from earlier
rc=7.5)
mmatoms.calc = calc
mmatoms.calc.initialize(mmatoms)
# LJ arrays for the 'QM' subsystem
sig_qm = np.array([sigNa, sigNa])
eps_qm = np.array([epsNa, epsNa])
# For the MM subsystem, tuple of arrays (counterion, water)
sig_mm = (np.array([sigNa]), sig2)
eps_mm = (np.array([epsNa]), eps2)
lj = LJInteractionsGeneral(sig_qm, eps_qm, sig_mm, eps_mm, 2)
ecomb, fcomb1, fcomb2 = lj.calculate(faux_qm, mmatoms, np.array([0, 0, 0]))
# This should give the same result as if not using CombineMM, on a sum
# of these systems:
# A: All the Na atoms in the 'QM' region
# B: LJInteractions between the 'QM' Na and the 'MM' Na
# C: -LJinteractions between the 'MM' Na and the 'MM' Water
# A:
mmatoms = dimer
mmatoms.calc = []
sig_qm = np.concatenate((sig_qm, sig_qm))
eps_qm = np.concatenate((eps_qm, eps_qm))
sig_mm = sig_mm[1]
eps_mm = eps_mm[1]
lj = LJInteractionsGeneral(sig_qm, eps_qm, sig_mm, eps_mm, 4)
ea, fa1, fa2 = lj.calculate(faux_qm + ions, mmatoms, np.array([0, 0, 0]))
# B:
lj = LJInteractionsGeneral(sig_qm[:2], eps_qm[:2], sig_qm[:2], eps_qm[:2],
2, 2)
eb, fb1, fb2, = lj.calculate(faux_qm, ions, np.array([0, 0, 0]))
# C:
lj = LJInteractionsGeneral(sig_qm[:2], eps_qm[:2], sig_mm, eps_mm, 2, 3)
ec, fc1, fc2, = lj.calculate(ions, dimer, np.array([0, 0, 0]))
assert ecomb - (ea + eb) + ec == 0
epsilon,
rc=rc,
width=1.0)
F2 = dimer.get_forces()
dF = F1 - F2
print(TIPnP)
print(dF)
assert abs(dF).max() < 1e-8
# Also check a TIP3P/TIP4P combination against numerical forces:
eps1 = np.array([eps3, 0, 0])
sig1 = np.array([sig3, 0, 0])
eps2 = np.array([eps4, 0, 0])
sig2 = np.array([sig4, 0, 0])
dimer.calc = CombineMM([0, 1, 2], 3, 3, TIP3P(rc, 1.0), TIP4P(rc, 1.0), sig1,
eps1, sig2, eps2, rc, 1.0)
F2 = dimer.get_forces()
Fn = dimer.calc.calculate_numerical_forces(dimer, 1e-7)
dF = F2 - Fn
print('TIP3P/TIP4P')
print(dF)
assert abs(dF).max() < 1e-8
# LJInteractionsGeneral with CombineMM.
# As it is used within EIQMMM, but avoiding long calculations for tests.
# Total system is a unit test system comprised of:
# 2 Na ions playing the role of a 'QM' subsystem
# 2 Na ions as the 'Counterions'
# 2 Water molecules
[0, rOH * np.cos(x), -rOH * np.sin(x)]]
atoms = Atoms('OH2', positions=pos)
vol = ((18.01528 / 6.022140857e23) / (0.9982 / 1e24))**(1 / 3.)
atoms.set_cell((vol, vol, vol))
atoms.center()
atoms = atoms.repeat((3, 3, 3))
atoms.set_pbc(True)
# RATTLE-type constraints on O-H1, O-H2, H1-H2.
atoms.constraints = FixBondLengths([(3 * i + j, 3 * i + (j + 1) % 3)
for i in range(3**3) for j in [0, 1, 2]])
tag = 'tip3p_27mol_equil'
atoms.calc = TIP3P(rc=4.5)
md = Langevin(atoms,
1 * units.fs,
temperature=300 * units.kB,
friction=0.01,
logfile=tag + '.log')
traj = Trajectory(tag + '.traj', 'w', atoms)
md.attach(traj.write, interval=1)
md.run(4000)
# Repeat box and equilibrate further.
tag = 'tip3p_216mol_equil'
atoms.set_constraint() # repeat not compatible with FixBondLengths currently.
atoms = atoms.repeat((2, 2, 2))
atoms.constraints = FixBondLengths([(3 * i + j, 3 * i + (j + 1) % 3)