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x_error_force_constant_and_frequencies_selective_subspace

esta.phonon.x_error_force_constant_and_frequencies_selective_subspace

get_forces_dict(atommove)

get forces fron qe output files with + and - displacements and store them in dictionary with indices indication atoms moving index, atom shift index, and displacemet(+ or -)

get_forces_dict_parta(atommove)

get forces fron qe output files with + and - displacements and store them in dictionary with indices indication atoms moving index, atom shift index, and displacemet(+ or -)

get_idatm_iddir_iddispl(atommove)

get a list of 'idatm-iddir-iddispl' idatm: atom id iddir : atom move direction index iddispl: + or - shift of atoms

atom_direction_shift ==> id atom, id direction, id shift

get_forces_minus(atommove, forces_dict, atom_direction_shift)

extract forces from forces_dict for minus (id=0) displacement

get_forces_plus(atommove, forces_dict, atom_direction_shift)

extract forces from forces_dict for plus (id=1) displacement

get_symmetrized_force_constant_matrix(fcMatrx, atommove)

symmetrize force constant matrix fc(iat, ia, jat, ja)

return (fc(iat, ia, jat, ja) + fc(jat, ja, iat, ia))/2

get_asr(fcMatrix, atommove)

apply accoustic sum rule on the force constant matrix

see Xavier gonze PRB paper:

XAVIER GONZE AND CHANGYOL LEE PHYSICAL REVIEW B VOLUME 55, NUMBER 16 15 APRIL 1997-I

specifically see equations: 44 and 45.. good luck ..read whole paper..sk!!

write_forces(force_row, ldisp)

may be you need to add ... atoms parameter in the call ..

write forces rows to a file NOTE: only for - and + displacement

todo : for writing central diff force constant .. no need of ldisp tag

get_sqrt_mass_array(label)

for given atomic symbols, return correspoinding masses in amu

get_dynamical_matrix(atommove, sqrt_mass_array, forceconstant)

getting dynamical matrix from force constant matrix at q=0 point

NOTE: for q=0 

   1. dynmat = fc matric/ sqrt(mass1)/ sqrt(mass2)

   2. dynmat in q space = dynmat in R space; see equation 7 in 
           paper of Ab initio calculation of phonon dispersions in semiconductors
           prb. Paolo Giannozzi et al. 1991

get_eigen(dynamatical_matrix)

dynamical matrix is hermitian matrix .. try taking it Hermitian matrix instead of general matrix