EPW Forum

Dear all
When I calculate the Eliashberg spectral function in EPW and PHonon(the module in QE), I found they are different. Especially, the DOS near 0 frequency jumps sharply in EPW but not in PHonon. And the lambda caculated in EPW seems too large, so strange! Maybe something wrong in the Phonon spectrum calculated in ph.x? Since the TA mode is too soft near gamma point? The pictures are showed in the attachments. Can anyone tell me why? and I should I do to get the right result.

Hi xiaming,

Which "electron_phonon" method are you using in the PHonon code? In my experience, electron_phonon ='interpolated' in the PHonon code gives the a2F in very good agreement with the EPW code but electron_phonon ='simple' does not. In the electron_phonon ='interpolated' method, it uses the interpolation scheme both in k- and q-grid so that your a2F agrees well with the EPW code.

Sometimes the artifact (soft mode) you see around the Gamma point may cause you to jump near zero frequency in EPW. I would suggest increasing the q-mesh along the in-plane direction to calculate phonon so that your artifact can be corrected near Gamma, and hopefully, your EPW results will also be meaningful. Also, please make sure that your phonon is converged with respect to k- and q-mesh.

Hope this helps.

Best
Gyanu
Binghamton University