Re: [Phonopy-users] freq vs q-distance as a table

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

Hi,

I'm sorry for that I didn't mention in detail about it. Currently,
get_band_structure is defined as follows:

    def get_band_structure(self):
        band = self._band_structure
        return (band.get_qpoints(),
                band.get_distances(),
                band.get_frequencies(),
                band.get_eigenvectors())

So, you would obtain a list (tuple) of qpoints, distances,
frequencies, eigenvectors.
Now each element of this list is a set of quantities of band segments.
The unit conversion factor is multiplied in the phonopy module.
VasptoTHz is the default value of it, so you don't need to multiply by
yourself if your unit conversion factor is this.

An example of code script is shown below.

bands = phonon.get_band_structure()
distances = bands[1]
frequencies = bands[2]
qpoints = bands[0]
for (qs_at_segments,
     dists_at_segments,
     freqs_at_segments) in zip(qpoints, distances, frequencies):

    for q, d, f in zip(qs_at_segments,
                       dists_at_segments,
                       freqs_at_segments):
        print "# %f %f %f" % tuple(q)
        print d, ("%f " * len(f)) % tuple(f)

I attach an example for workable with example/Al2O3, too.

Togo


On Thu, Oct 4, 2012 at 4:40 AM, Iyad AL-QASIR <iy...@gm...> wrote:
> Dear Phonopy Users,
>
> Moving from Phonpy-1.3 to Phonopy-1.5 some changes ( toward better) have
> been made.
>
> I am using mainly phonopy as a python module. In my *.py file to get the
> phonon dispersions ( Freq vs q-distance), I had this part of code do that
> (Thanks to A. Togo he helped in that),
>
> phonon.set_band_structure(bands,is_eigenvectors=True)
> dispersion=phonon.get_band_structure()
> phonon.write_yaml_band_structure()
> distances=dispersion[0]
> eigenvalues=dispersion[2]
> for eigs_at_index in eigenvalues.T:
>     freq=[-np.sqrt(-x) if x<0 else np.sqrt(x) for x in eigs_at_index]
>     for d,f in zip(distances, freq):
>         print d,f*VasptoTHz
>     print
>     print
>
>
> However, in Phonopy-1.5 this will not work since some changes made in order
> of distances, eigen values, ...
>
> It would be grate if the above piece of code is corrected so it will give me
> the dispersions in a table as a function of q-distance.
>
> Thanks,
> ___________________________
> IYAD I. AL-QASIR, PhD
> Postdoc Research Associate
>
> X-Ray and Neutron Scattering and Spectroscopy Group
> Materials Science and Technology Division
> Oak Ridge National Lab
> Oak Ridge, TN
>
>
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-- 
Atsushi Togo
http://atztogo.users.sourceforge.net/
atz...@gm...