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import numpy as np
import ase.units as u
from ase.vibrations.raman import Raman, RamanPhonons
from ase.vibrations.resonant_raman import ResonantRaman
from ase.calculators.excitation_list import polarizability
class Placzek(ResonantRaman):
"""Raman spectra within the Placzek approximation."""
def __init__(self, *args, **kwargs):
self._approx = 'PlaczekAlpha'
ResonantRaman.__init__(self, *args, **kwargs)
def set_approximation(self, value):
raise ValueError('Approximation can not be set.')
def read_excitations(self):
"""Read excitations from files written"""
self.ex0E_p = None # mark as read
self.exm_r = []
self.exp_r = []
for a, i in zip(self.myindices, self.myxyz):
exname = '%s.%d%s-' % (self.exname, a, i) + self.exext
self.log('reading ' + exname)
self.exm_r.append(self.exobj.read(exname, **self.exkwargs))
exname = '%s.%d%s+' % (self.exname, a, i) + self.exext
self.log('reading ' + exname)
self.exp_r.append(self.exobj.read(exname, **self.exkwargs))
def electronic_me_Qcc(self, omega, gamma=0):
self.calculate_energies_and_modes()
self.timer.start('init')
V_rcc = np.zeros((self.ndof, 3, 3), dtype=complex)
pre = 1. / (2 * self.delta)
pre *= u.Hartree * u.Bohr # e^2Angstrom^2 / eV -> Angstrom^3
om = omega
if gamma:
om += 1j * gamma
self.timer.stop('init')
self.timer.start('alpha derivatives')
for i, r in enumerate(self.myr):
V_rcc[r] = pre * (
polarizability(self.exp_r[i], om,
form=self.dipole_form, tensor=True) -
polarizability(self.exm_r[i], om,
form=self.dipole_form, tensor=True))
self.comm.sum(V_rcc)
self.timer.stop('alpha derivatives')
return self.map_to_modes(V_rcc)
class PlaczekStatic(Raman):
def read_excitations(self):
"""Read excitations from files written"""
self.al0_rr = None # mark as read
self.alm_rr = []
self.alp_rr = []
for a, i in zip(self.myindices, self.myxyz):
exname = '%s.%d%s-' % (self.exname, a, i) + self.exext
self.log('reading ' + exname)
self.alm_rr.append(np.loadtxt(exname))
exname = '%s.%d%s+' % (self.exname, a, i) + self.exext
self.log('reading ' + exname)
self.alp_rr.append(np.loadtxt(exname))
def electronic_me_Qcc(self):
self.calculate_energies_and_modes()
self.timer.start('init')
V_rcc = np.zeros((self.ndof, 3, 3), dtype=complex)
pre = 1. / (2 * self.delta)
pre *= u.Hartree * u.Bohr # e^2Angstrom^2 / eV -> Angstrom^3
self.timer.stop('init')
self.timer.start('alpha derivatives')
for i, r in enumerate(self.myr):
V_rcc[r] = pre * (self.alp_rr[i] - self.alm_rr[i])
self.comm.sum(V_rcc)
self.timer.stop('alpha derivatives')
return self.map_to_modes(V_rcc)
class PlaczekStaticPhonons(RamanPhonons, PlaczekStatic):
pass
class Profeta(ResonantRaman):
"""Profeta type approximations.
Reference
---------
Mickael Profeta and Francesco Mauri
Phys. Rev. B 63 (2000) 245415
"""
def __init__(self, *args, **kwargs):
self.set_approximation(kwargs.pop('approximation', 'Profeta'))
self.nonresonant = kwargs.pop('nonresonant', True)
ResonantRaman.__init__(self, *args, **kwargs)
def set_approximation(self, value):
approx = value.lower()
if approx in ['profeta', 'placzek', 'p-p']:
self._approx = value
else:
raise ValueError('Please use "Profeta", "Placzek" or "P-P".')
def electronic_me_profeta_rcc(self, omega, gamma=0.1,
energy_derivative=False):
"""Raman spectra in Profeta and Mauri approximation
Returns
-------
Electronic matrix element, unit Angstrom^2
"""
self.calculate_energies_and_modes()
self.timer.start('amplitudes')
self.timer.start('init')
V_rcc = np.zeros((self.ndof, 3, 3), dtype=complex)
pre = 1. / (2 * self.delta)
pre *= u.Hartree * u.Bohr # e^2Angstrom^2 / eV -> Angstrom^3
self.timer.stop('init')
def kappa_cc(me_pc, e_p, omega, gamma, form='v'):
"""Kappa tensor after Profeta and Mauri
PRB 63 (2001) 245415"""
k_cc = np.zeros((3, 3), dtype=complex)
for p, me_c in enumerate(me_pc):
me_cc = np.outer(me_c, me_c.conj())
k_cc += me_cc / (e_p[p] - omega - 1j * gamma)
if self.nonresonant:
k_cc += me_cc.conj() / (e_p[p] + omega + 1j * gamma)
return k_cc
self.timer.start('kappa')
mr = 0
for a, i, r in zip(self.myindices, self.myxyz, self.myr):
if not energy_derivative < 0:
V_rcc[r] += pre * (
kappa_cc(self.expm_rpc[mr], self.ex0E_p,
omega, gamma, self.dipole_form) -
kappa_cc(self.exmm_rpc[mr], self.ex0E_p,
omega, gamma, self.dipole_form))
if energy_derivative:
V_rcc[r] += pre * (
kappa_cc(self.ex0m_pc, self.expE_rp[mr],
omega, gamma, self.dipole_form) -
kappa_cc(self.ex0m_pc, self.exmE_rp[mr],
omega, gamma, self.dipole_form))
mr += 1
self.comm.sum(V_rcc)
self.timer.stop('kappa')
self.timer.stop('amplitudes')
return V_rcc
def electronic_me_Qcc(self, omega, gamma):
self.read()
Vel_rcc = np.zeros((self.ndof, 3, 3), dtype=complex)
approximation = self.approximation.lower()
if approximation == 'profeta':
Vel_rcc += self.electronic_me_profeta_rcc(omega, gamma)
elif approximation == 'placzek':
Vel_rcc += self.electronic_me_profeta_rcc(omega, gamma, True)
elif approximation == 'p-p':
Vel_rcc += self.electronic_me_profeta_rcc(omega, gamma, -1)
else:
raise RuntimeError(
'Bug: call with {0} should not happen!'.format(
self.approximation))
return self.map_to_modes(Vel_rcc)
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