def __init__(self,
calc,
gwfile,
filename=None,
kpts=[0],
bands=None,
structure=None,
d=None,
layer=0,
dW_qw=None,
qqeh=None,
wqeh=None,
txt=sys.stdout,
world=mpi.world,
domega0=0.025,
omega2=10.0,
eta=0.1,
include_q0=True,
metal=False):
"""
Class for calculating quasiparticle energies of van der Waals
heterostructures using the GW approximation for the self-energy.
The quasiparticle energy correction due to increased screening from
surrounding layers is obtained from the QEH model.
Parameters:
calc: str or PAW object
GPAW calculator object or filename of saved calculator object.
gwfile: str
name of gw results file from the monolayer calculation
filename: str
filename for gwqeh output
kpts: list
List of indices of sthe IBZ k-points to calculate the quasi
particle energies for. Set to [0] by default since the QP
correction is generally the same for all k.
bands: tuple
Range of band indices, like (n1, n2+1), to calculate the quasi
particle energies for. Note that the second band index is not
included. Should be the same as used for the GW calculation.
structure: list of str
Heterostructure set up. Each entry should consist of number of
layers + chemical formula.
For example: ['3H-MoS2', graphene', '10H-WS2'] gives 3 layers of
H-MoS2, 1 layer of graphene and 10 layers of H-WS2.
The name of the layers should correspond to building block files:
"<name>-chi.pckl" in the local repository.
d: array of floats
Interlayer distances for neighboring layers in Ang.
Length of array = number of layers - 1
layer: int
index of layer to calculate QP correction for.
dW_qw: 2D array of floats dimension q X w
Change in screened interaction. Should be set to None to calculate
dW directly from buildingblocks.
qqeh: array of floats
q-grid used for dW_qw (only needed if dW is given by hand).
wqeh: array of floats
w-grid used for dW_qw. So far this have to be the same as for the
GWQEH calculation. (only needed if dW is given by hand).
domega0: float
Minimum frequency step (in eV) used in the generation of the non-
linear frequency grid.
omega2: float
Control parameter for the non-linear frequency grid, equal to the
frequency where the grid spacing has doubled in size.
eta: float
Broadening parameter.
include_q0: bool
include q=0 in W or not. if True an integral arround q=0 is
performed, if False the q=0 contribution is set to zero.
metal: bool
If True, the point at q=0 is omitted when averaging the screened
potential close to q=0.
"""
self.gwfile = gwfile
self.inputcalc = calc
# Set low ecut in order to use PairDensity object since only
# G=0 is needed.
self.ecut = 1.
PairDensity.__init__(self,
calc,
ecut=self.ecut,
world=world,
txt=filename + '.txt')
self.filename = filename
self.ecut /= Hartree
self.eta = eta / Hartree
self.domega0 = domega0 / Hartree
self.omega2 = omega2 / Hartree
self.kpts = list(select_kpts(kpts, self.calc))
if bands is None:
bands = [0, self.nocc2]
self.bands = bands
b1, b2 = bands
self.shape = shape = (self.calc.wfs.nspins, len(self.kpts), b2 - b1)
self.eps_sin = np.empty(shape) # KS-eigenvalues
self.f_sin = np.empty(shape) # occupation numbers
self.sigma_sin = np.zeros(shape) # self-energies
self.dsigma_sin = np.zeros(shape) # derivatives of self-energies
self.Z_sin = None # renormalization factors
self.qp_sin = None
self.Qp_sin = None
self.ecutnb = 150 / Hartree
vol = abs(np.linalg.det(self.calc.wfs.gd.cell_cv))
self.vol = vol
self.nbands = min(self.calc.get_number_of_bands(),
int(vol * (self.ecutnb)**1.5 * 2**0.5 / 3 / pi**2))
self.nspins = self.calc.wfs.nspins
kd = self.calc.wfs.kd
self.mysKn1n2 = None # my (s, K, n1, n2) indices
self.distribute_k_points_and_bands(b1, b2, kd.ibz2bz_k[self.kpts])
# Find q-vectors and weights in the IBZ:
assert -1 not in kd.bz2bz_ks
offset_c = 0.5 * ((kd.N_c + 1) % 2) / kd.N_c
bzq_qc = monkhorst_pack(kd.N_c) + offset_c
self.qd = KPointDescriptor(bzq_qc)
self.qd.set_symmetry(self.calc.atoms, kd.symmetry)
# frequency grid
omax = self.find_maximum_frequency()
self.omega_w = frequency_grid(self.domega0, self.omega2, omax)
self.nw = len(self.omega_w)
self.wsize = 2 * self.nw
# Calculate screened potential of Heterostructure
if dW_qw is None:
try:
self.qqeh, self.wqeh, dW_qw = pickle.load(
open(filename + '_dW_qw.pckl', 'rb'))
except:
dW_qw = self.calculate_W_QEH(structure, d, layer)
else:
self.qqeh = qqeh
self.wqeh = None # wqeh
self.dW_qw = self.get_W_on_grid(dW_qw,
include_q0=include_q0,
metal=metal)
assert self.nw == self.dW_qw.shape[1], \
('Frequency grids doesnt match!')
self.htp = HilbertTransform(self.omega_w, self.eta, gw=True)
self.htm = HilbertTransform(self.omega_w, -self.eta, gw=True)
self.complete = False
self.nq = 0
if self.load_state_file():
if self.complete:
print('Self-energy loaded from file', file=self.fd)
def __init__(self, calc, filename='gw',
kpts=None, bands=None, nbands=None, ppa=False,
wstc=False,
ecut=150.0, eta=0.1, E0=1.0 * Hartree,
domega0=0.025, omega2=10.0,
world=mpi.world):
PairDensity.__init__(self, calc, ecut, world=world,
txt=filename + '.txt')
self.filename = filename
ecut /= Hartree
self.ppa = ppa
self.wstc = wstc
self.eta = eta / Hartree
self.E0 = E0 / Hartree
self.domega0 = domega0 / Hartree
self.omega2 = omega2 / Hartree
print(' ___ _ _ _ ', file=self.fd)
print(' | || | | |', file=self.fd)
print(' | | || | | |', file=self.fd)
print(' |__ ||_____|', file=self.fd)
print(' |___| ', file=self.fd)
print(file=self.fd)
self.kpts = select_kpts(kpts, self.calc)
if bands is None:
bands = [0, self.nocc2]
self.bands = bands
b1, b2 = bands
self.shape = shape = (self.calc.wfs.nspins, len(self.kpts), b2 - b1)
self.eps_sin = np.empty(shape) # KS-eigenvalues
self.f_sin = np.empty(shape) # occupation numbers
self.sigma_sin = np.zeros(shape) # self-energies
self.dsigma_sin = np.zeros(shape) # derivatives of self-energies
self.vxc_sin = None # KS XC-contributions
self.exx_sin = None # exact exchange contributions
self.Z_sin = None # renormalization factors
if nbands is None:
nbands = int(self.vol * ecut**1.5 * 2**0.5 / 3 / pi**2)
self.nbands = nbands
kd = self.calc.wfs.kd
self.mysKn1n2 = None # my (s, K, n1, n2) indices
self.distribute_k_points_and_bands(b1, b2, kd.ibz2bz_k[self.kpts])
# Find q-vectors and weights in the IBZ:
assert -1 not in kd.bz2bz_ks
offset_c = 0.5 * ((kd.N_c + 1) % 2) / kd.N_c
bzq_qc = monkhorst_pack(kd.N_c) + offset_c
self.qd = KPointDescriptor(bzq_qc)
self.qd.set_symmetry(self.calc.atoms, self.calc.wfs.setups,
usesymm=self.calc.input_parameters.usesymm,
N_c=self.calc.wfs.gd.N_c)
assert self.calc.wfs.nspins == 1
def __init__(self, calc, filename='gw',
kpts=None, bands=None, nbands=None, ppa=False,
wstc=False,
ecut=150.0, eta=0.1, E0=1.0 * Hartree,
domega0=0.025, omega2=10.0,
nblocks=1, savew=False,
world=mpi.world):
if world.rank != 0:
txt = devnull
else:
txt = open(filename + '.txt', 'w')
p = functools.partial(print, file=txt)
p(' ___ _ _ _ ')
p(' | || | | |')
p(' | | || | | |')
p(' |__ ||_____|')
p(' |___|')
p()
PairDensity.__init__(self, calc, ecut, world=world, nblocks=nblocks,
txt=txt)
self.filename = filename
self.savew = savew
ecut /= Hartree
self.ppa = ppa
self.wstc = wstc
self.eta = eta / Hartree
self.E0 = E0 / Hartree
self.domega0 = domega0 / Hartree
self.omega2 = omega2 / Hartree
self.kpts = select_kpts(kpts, self.calc)
if bands is None:
bands = [0, self.nocc2]
self.bands = bands
b1, b2 = bands
self.shape = shape = (self.calc.wfs.nspins, len(self.kpts), b2 - b1)
self.eps_sin = np.empty(shape) # KS-eigenvalues
self.f_sin = np.empty(shape) # occupation numbers
self.sigma_sin = np.zeros(shape) # self-energies
self.dsigma_sin = np.zeros(shape) # derivatives of self-energies
self.vxc_sin = None # KS XC-contributions
self.exx_sin = None # exact exchange contributions
self.Z_sin = None # renormalization factors
if nbands is None:
nbands = int(self.vol * ecut**1.5 * 2**0.5 / 3 / pi**2)
self.nbands = nbands
p()
p('Quasi particle states:')
if kpts is None:
p('All k-points in IBZ')
else:
kptstxt = ', '.join(['{0:d}'.format(k) for k in self.kpts])
p('k-points (IBZ indices): [' + kptstxt + ']')
p('Band range: ({0:d}, {1:d})'.format(b1, b2))
p()
p('Computational parameters:')
p('Plane wave cut-off: {0:g} eV'.format(self.ecut * Hartree))
p('Number of bands: {0:d}'.format(self.nbands))
p('Broadening: {0:g} eV'.format(self.eta * Hartree))
kd = self.calc.wfs.kd
self.mysKn1n2 = None # my (s, K, n1, n2) indices
self.distribute_k_points_and_bands(b1, b2, kd.ibz2bz_k[self.kpts])
# Find q-vectors and weights in the IBZ:
assert -1 not in kd.bz2bz_ks
offset_c = 0.5 * ((kd.N_c + 1) % 2) / kd.N_c
bzq_qc = monkhorst_pack(kd.N_c) + offset_c
self.qd = KPointDescriptor(bzq_qc)
self.qd.set_symmetry(self.calc.atoms, kd.symmetry)
assert self.calc.wfs.nspins == 1