I am trying to calculate Raman Spectrum of monolayer MoS2. But I only see one peak around 396 cm^-1 whereas the experimental peaks are around 385 and 403 cm^-1. Kindly clarify the issue. I also tried changing polarization direction to 100. That gives three peaks but incorrect also. The script is as follows:
# %% Molybdenite (1)
# Set up lattice
lattice = Hexagonal(3.1604*Angstrom, 40.0*Angstrom)
# Define elements
elements = [Molybdenum, Sulfur, Sulfur]
# Define coordinates
fractional_coordinates = [[ 0.333333333333, 0.666666666667, 0.5 ],
[ 0.666666666667, 0.333333333333, 0.460348625 ],
[ 0.666666666667, 0.333333333333, 0.539651375 ]]
# Set up configuration
molybdenite_1 = BulkConfiguration(
bravais_lattice=lattice,
elements=elements,
fractional_coordinates=fractional_coordinates
)
molybdenite_1_name = "Molybdenite (1)"
# %% Set LCAOCalculator
# %% LCAOCalculator
# ----------------------------------------
# Basis Set
# ----------------------------------------
basis_set = [
BasisGGASG15.Sulfur_High,
BasisGGASG15.Molybdenum_High,
]
k_point_sampling = MonkhorstPackGrid(na=13, nb=13)
numerical_accuracy_parameters = NumericalAccuracyParameters(
density_mesh_cutoff=120.0 * Hartree, k_point_sampling=k_point_sampling
)
calculator = LCAOCalculator(
basis_set=basis_set,
numerical_accuracy_parameters=numerical_accuracy_parameters,
checkpoint_handler=NoCheckpointHandler,
)
# %% Set Calculator
molybdenite_1.setCalculator(calculator)
molybdenite_1.update()
nlsave('Raman_SG15High.hdf5', molybdenite_1)
# %% OptimizeGeometry
restart_strategy = RestartFromTrajectory(
trajectory_filename='Raman_SG15High.hdf5',
object_id='optimize_trajectory',
)
optimized_configuration = OptimizeGeometry(
configuration=molybdenite_1,
max_forces=0.01 * eV / Angstrom,
constraints=[FixStrain(True, True, True)],
trajectory_filename='Raman_SG15High.hdf5',
trajectory_object_id='optimize_trajectory',
optimize_cell=False,
restart_strategy=restart_strategy,
)
nlsave('Raman_SG15High.hdf5', optimized_configuration, object_id='optgeom')
# %% DynamicalMatrix
dynamical_matrix = DynamicalMatrix(
configuration=optimized_configuration,
filename='Raman_SG15High.hdf5',
object_id='dm',
calculator=calculator,
)
dynamical_matrix.update()
# %% SusceptibilityDerivatives
kpoints = MonkhorstPackGrid(na=23, nb=23, nc=2)
susceptibility_derivatives = SusceptibilityDerivatives(
configuration=optimized_configuration,
filename='Raman_SG15High.hdf5',
object_id='sd',
kpoints=kpoints,
)
susceptibility_derivatives.update()
# %% RamanSpectrum
raman_spectrum = RamanSpectrum(
configuration=optimized_configuration,
dynamical_matrix=dynamical_matrix,
susceptibility_derivatives=susceptibility_derivatives,
polarization_in=(0.0, 0.0, 1.0),
polarization_out=(0.0, 0.0, 1.0),
number_of_angles=None,
polarization_orthogonal=None,
)
nlsave('Raman_SG15High.hdf5', raman_spectrum)
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