def get_elph_elements(atoms,
gpw_name,
calc_fd,
sc=(1, 1, 1),
basename=None,
phononname='phonon'):
"""
Evaluates the dipole transition matrix elements
Input
----------
params_fd : Calculation parameters used for the phonon calculation
sc (tuple): Supercell, default is (1,1,1) used for gamma phonons
basename : If you want give a specific name (gqklnn_{}.pckl)
Output
----------
gqklnn.pckl, the electron-phonon matrix elements
"""
from ase.phonons import Phonons
from gpaw.elph.electronphonon import ElectronPhononCoupling
calc_gs = GPAW(gpw_name)
world = calc_gs.wfs.world
#calc_fd = GPAW(**params_fd)
calc_gs.initialize_positions(atoms)
kpts = calc_gs.get_ibz_k_points()
nk = len(kpts)
gamma_kpt = [[0, 0, 0]]
nbands = calc_gs.wfs.bd.nbands
qpts = gamma_kpt
# calc_fd.get_potential_energy() # XXX needed to initialize C_nM ??????
# Phonon calculation, We'll read the forces from the elph.run function
# This only looks at gamma point phonons
ph = Phonons(atoms=atoms, name=phononname, supercell=sc)
ph.read()
frequencies, modes = ph.band_structure(qpts, modes=True)
if world.rank == 0:
print("Phonon frequencies are loaded.")
# Find el-ph matrix in the LCAO basis
elph = ElectronPhononCoupling(atoms, calc=None, supercell=sc)
elph.set_lcao_calculator(calc_fd)
elph.load_supercell_matrix()
if world.rank == 0:
print("Supercell matrix is loaded")
# Non-root processes on GD comm seem to be missing kpoint data.
assert calc_gs.wfs.gd.comm.size == 1, "domain parallelism not supported" # not sure how to fix this, sorry
gcomm = calc_gs.wfs.gd.comm
kcomm = calc_gs.wfs.kd.comm
if gcomm.rank == 0:
# Find the bloch expansion coefficients
c_kn = np.empty((nk, nbands, calc_gs.wfs.setups.nao), dtype=complex)
for k in range(calc_gs.wfs.kd.nibzkpts):
c_k = calc_gs.wfs.collect_array("C_nM", k, 0)
if kcomm.rank == 0:
c_kn[k] = c_k
kcomm.broadcast(c_kn, 0)
# And we finally find the electron-phonon coupling matrix elements!
g_qklnn = elph.bloch_matrix(c_kn=c_kn,
kpts=kpts,
qpts=qpts,
u_ql=modes)
if world.rank == 0:
print("Saving the elctron-phonon coupling matrix")
np.save("gqklnn{}.npy".format(make_suffix(basename)),
np.array(g_qklnn))
'basis': 'dzp',
'symmetry': {
'point_group': False
},
'xc': 'PBE'
}
elph_calc = GPAW(**parameters)
atoms.set_calculator(elph_calc)
atoms.get_potential_energy()
gamma_bands = elph_calc.wfs.kpt_u[0].C_nM
elph = ElectronPhononCoupling(atoms,
elph_calc,
supercell=supercell,
calculate_forces=True)
elph.run()
parameters['parallel'] = {'domain': 1}
elph_calc = GPAW(**parameters)
elph = ElectronPhononCoupling(atoms, calc=None, supercell=supercell)
elph.set_lcao_calculator(elph_calc)
elph.calculate_supercell_matrix(dump=1)
ph = Phonons(atoms=atoms, name='phonons', supercell=supercell, calc=None)
ph.read()
kpts = [[0, 0, 0]]
frequencies, modes = ph.band_structure(kpts, modes=True)
c_kn = np.array([[gamma_bands[0]]])
g_qklnn = elph.bloch_matrix(c_kn=c_kn, kpts=kpts, qpts=kpts, u_ql=modes)