nbands=8*3,
width=0.01,
kpts=(2, 2, 2),
convergence={'eigenstates': 1e-9}
)
# Phonopy pre-process
print "------"
print "Phonon"
print "------"
# 1st arg. is the input unit cell.
# 2nd arg. is the supercell lattice relative to the unit cell.
# 'distance' is the distance of displacements.
# Default symmetry tolerance is 1e-5 in fractional coordinates.
phonon = Phonopy(bulk, [[1,0,0],[0,1,0],[0,0,1]], distance=0.01)
phonon.print_displacements()
supercells = phonon.get_supercells_with_displacements()
# Force calculations by calculator
set_of_forces = []
for scell in supercells:
cell = Atoms( symbols=scell.get_chemical_symbols(),
scaled_positions=scell.get_scaled_positions(),
cell=scell.get_cell(),
pbc=True )
cell.set_calculator(calc)
forces = cell.get_forces()
drift_force = forces.sum(axis=0)
print " ---------------------------------"
print " ", "%11.5f"*3 % tuple(drift_force)
# Simple translational invariance
bulk = diamond(a, 14)
pot = Potential('IP SW')
bulk.set_calculator(pot)
# Phonopy pre-process
print "------"
print "Phonon"
print "------"
# 1st arg. is the input unit cell.
# 2nd arg. is the supercell lattice relative to the unit cell.
# 'distance' is the distance of displacements.
# Default symmetry tolerance is 1e-5 in fractional coordinates.
phonon = Phonopy(bulk, [[1, 0, 0], [0, 1, 0], [0, 0, 1]],
distance=0.01,
factor=VaspToTHz)
phonon.print_displacements()
supercells = phonon.get_supercells_with_displacements()
# Do force calculations using QUIP Potential
set_of_forces = []
for cell in supercells:
forces = pot.get_forces(cell)
drift_force = forces.sum(axis=0)
print " ---------------------------------"
print " ", "%11.5f" * 3 % tuple(drift_force)
# Simple translational invariance
for force in forces:
force -= drift_force / forces.shape[0]
set_of_forces.append(forces)
# Phonopy post-process
