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

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

Hi,

It's implied by the formula. There is no standard direction.

Togo

On Thu, Apr 29, 2021 at 11:42 AM Thomas Harrelson <tha...@gm...> wrote:
>
> I see, so by default, setting the nac_params does not turn on the non-analytical term correction when calculating the phonons in mesh mode? Is there a standard direction that is typically used, or does the direction change the convergence rates, and thus any direction can be used?
>
> On Tue, Apr 27, 2021 at 8:06 PM Atsushi Togo <atz...@gm...> wrote:
>>
>> Maybe also, https://github.com/phonopy/phono3py/blob/5c66ad0a47ec349aa117f3f75b841242c6171d58/phono3py/api_phono3py.py#L926
>>
>> Togo
>>
>> On Wed, Apr 28, 2021 at 12:04 PM Atsushi Togo <atz...@gm...> wrote:
>> >
>> > 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
>>
>>
>>
>> --
>> Atsushi Togo
>>
>>
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-- 
Atsushi Togo