Re: [Phonopy-users] phonopy and phono3py

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

Hi,

> I  was wondering whether there is any  utility  to  determine  the
> principal  axis  for plotting the phonon  dispersion  using  phonopy.
> For simple system  such as  FCC  structure  we  generally specify
> PRIMITIVE_AXIS = 0 1/2 1/2  1/2 0 1/2  1/2 1/2 0 in the band.conf  file.
> However, for complex system, is there any tool that  I  can use for this?

phonopy doesn't have it. If your crystal structure (POSCAR) is
standardized, the transformation matrix (PRIMITIVE_AXIS) is
determined. Possible choices for standardized unit cells in spglib
that phonopy relies on are listed here,
http://atztogo.github.io/spglib/definition.html#transformation-to-the-primitive-cell

> Secondly,  for  getting the  Gruneisen parameter, the gruneisen  script
> spits  out the  .yaml  file  from  where  we  can  grep the  qpoints and
> corresponding Gruneisen parameter  to  plot  using  gnuplot. However, the
> resultant plot  does  not  match  with  that  from  gruneisen  script when
> -p option is  used.

By my quick test, I couldn't confirm what you write. My script to
convert the data in gruneisen.yaml to gnuplot style is as follows:

import yaml

data = yaml.load(open("gruneisen.yaml"))
path = data['path'][0]['phonon']

d = []
b = []
g = []
for q in path:
    d.append(q['distance'])
    b.append([band['frequency'] for band in q['band']])
    g.append([band['gruneisen'] for band in q['band']])

for n in range(len(b[0])):
    for dist, freqs, grus in zip(d, b, g):
        print("%f %f %f" % (dist, freqs[n], grus[n]))
    print("")
    print("")

> Thirdly, if  I use  444 supercell for  harmonic  and 222 supercell for
> anharmonic  force  constants, the gruneisen parameter  can not  be plotted
> using  phono3py. Is there any  way out  to  take care of this?

I don't see what you mean.

Togo

>
>
> Thanks in  advance for your help.
> Best,
> Saikat
>
>
>
>
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-- 
Atsushi Togo
Elements Strategy Initiative for Structural Materials, Kyoto university
E-mail: atz...@gm...