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Phonon dispersion relation using phonopy

Phonon dispersion relation can be calculated using phonopy program. So you have to install phonopy before moving forward in this topic.

First, prepare pmdini and band.conf files. The band.conf file should be like the following,

ATOM_NAME = Si
DIM =  4  4  4
BAND = 0 0 0  1/2 0 1/2,  1/2 1/2 1  0 0 0  1/2 1/2 1/2

Here ATOM_NAME is necessary if you want to get correct frequency values in phonon dispersion graph. Only phonon frequencies correspond to the wave numbers given by BAND parameters are shown.

Users do not need to consider DIM, these values are automatically determined in the following command.

$ python /path/to/pmd2phonopy.py -c 4.0 pmdini

Then you can get a band output file out_band, so you can see a graph with gnuplot as,

$ gnuplot
gnuplot> plot "out_band" us 1:2 w l

image

And the figure below is phonon density-of-states (DOS) obtained by integrating phonon dispersion over k-space.

image