Phonon Dispersion Mismatch

[Agathyan]

Dear all,

I performed EPW of Si with the tutorial files. Band Structure of bands.x and epw.x matched.

But Phonon Dispersion of ph.x and epw.x didn't match neither magnitude or profile of the curves.

I had also got the absorption co-efficient onset around 0.5 (Band Gap = 0.5115 eV). I have attached the inputs and outputs. Could anyone explain why Phonons Dispersion didn't match?

Si_QE_EPW_PH.jpg (158.4 KiB) Viewed 211 times

si_qe_epw_BS_.jpg (142.94 KiB) Viewed 211 times

[Nina Girotto]

Dear Agathyan,

To me it seems that the two dispersions are plotted on different q-paths. Take a look at the q point coordinates inside the phband.freq and si.freq files, perhaps this helps explain the difference?

Best,

Nina.

[Shashi]

Dear Agathyna,

As Nina mentioned, the q-paths units are slightly different in EPW and phonon band structure.

If you add this tag q_in_cryst_coord=.true. in your matdyn.in file and then generate the dispersion file, this would resolve the path issues.

Regards,
Shashi