Re: [Phonopy-users] Problem with setting nac_params with Phono3py API

[Atsushi T. <atz...@gm...>]

Hi,

See https://phonopy.github.io/phono3py/command-options.html#q-direction-q-direction/

Togo

On Wed, Apr 28, 2021 at 11:44 AM Thomas Harrelson <tha...@gm...> wrote:
>
> I am attempting to use the Phono3py API to calculate the imaginary self energy, phonon frequency, and phonon eigenvector arrays for further analysis within a code. I'm using this for materials with optically active phonons, so the NAC terms need to be present. At the moment, I'm following the code in Si.py script in the examples folder:
>
> primitive = phono3py.get_phonon_primitive()
> nac_params = parse_BORN(primitive, filename="BORN")
> nac_params['factor'] = Hartree * Bohr
> phono3py.set_phph_interaction(nac_params=nac_params)
> data = phono3py.get_phonon_data()
>
> Since the set_phph_interaction is deprecated, I also tried:
> phono3py.nac_params = nac_params
> phono3py.init_phph_interaction()
>
> In both of the above cases, the program works for GaAs, but there is no apparent LO-TO splitting for the optical phonons at gamma (all optical frequencies are the same), indicating that no NAC method was used. The phono3py._interaction object has the nac_params correctly loaded within it. Also, it appears that phono3py._interaction._dm has all the nac_params as well. Then why is there no LO-TO splitting? Am I setting up the code incorrectly, or what am I missing?
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-- 
Atsushi Togo