EPW Forum

Hello,

No, EPW doesn't calculate the loss function and plasmon energy; for those you should use e.g. Yambo.
EPW implements the approach of https://journals.aps.org/prb/abstract/1 ... .94.115208 for calculating the el-plasmon self-energy in a degenerate semiconductor. The carrier concentration is given by 'nel' in the input.

Best wishes,
Carla

Hello,

There is also a term in the self-energy corresponding to phonon emission, which can be sizable also at lower temperature.

Carla

Dear Vahid, Direct ab initio calculations of the matrix elements using DFPT for selected q points, as done with ph.x in that example, include ALL kinds of e-ph interactions, including the polar one. When doing Wannier-Fourier interpolation starting from a relatively coarse BZ grid, the correct treat...

Dear Sai,
At those carrier concentrations the screening has no effect indeed.

Best,
Carla

Dear Sanjay, You cannot completely 'switch off' the Frohlich interaction, but if lpolar=.false. then the long-range part of the matrix element is not treated correctly, and essentially you cut much of it off your calculations. By the way, in case you haven't come across this paper, it might be inter...

Dear Elio,

That is correct in the approximation that the effect of doping is only to rigidly shift the Fermi level.

Best
Carla

Hi, If you set efermi_read=.true. the Fermi level used in EPW is the one you provided. The message 'The Fermi level will be determined with -30.00000 electrons' is a bit misleading, as it is written also in the case efermi_read=.true. It doesn't look like the wrong value of nelec should affect your ...

Dear Vinpandey,

For electron linewidth calculations one needs to perform an integral over the q wavevector, so to get the el. linewidth at any desired k point, a dense q grid is what you need.

Best,
Carla

Dear Max, I think that should be a good approximation, since the effect of vdw corrections in the dft calculations should be mainly at the relaxation level. Anyway, you can verify this by e.g. comparing the band structure that you obtain with and without vdw corrections, of course using the same rel...

Hi, The order of the phonon modes at arbitrary q points, in both QE and EPW, is just of ascending phonon frequencies, that is the character of the modes is not followed. The discontinuities are therefore due to phonon crossings (e.g. looking at phonon dispersions I see modes 3 and 4 swapping along G...