EPW Forum

Hi, The prefix.epb* files are calculated almost at the beginning of the EPW run. To store them on disk you use epbwrite=.true.; when restarting from existing prefix.epb* files you can set epbwrite=.false. and epbread=.true. You cannot break the calculation of the prefix.epb* files in multiple restar...

Hi Max, The internal units in Quantum Espresso and EPW are always (Rydberg) atomic units, where hbar=1, hence why you don't see it. It is correct that the 1/sqrt(m) is already included in g through the ph eigenmodes. To obtain the g on the left side of the equation you need to multiply epmatf with 1...

Hi, Indeed all the matrix element arrays (epmatf etc) do not include the 1/sqrt(omega_q) factors which appear in the definition of the matrix element. This is why, in order to get the matrix elements in [Ry], you always have to multiply by that factor as its done in print_gkk. Hope this helps, Carla

Hi, If I remember correctly you cannot compare directly the matrix elements stored in the 'epmatq'. Yes those are the matrix elements on the coarse k,q grid, however i) they don't contain the prefactor 1/sqrt(2\omega_q\nu) that you have if you use 'prtgkk' to output the matrix elements on the fine g...

Dear Anindya, I have never studied graphene myself but based on the literature and on some old posts on this forum (see e.g. http://epwforum.uk/viewtopic.php?f=3&t=367&start=0&hilit=graphene ) it looks like you might need a 24x24x1 k grid for the wannierization. This is not because your ...

Hi, It seems to me that you printed are not the matrix elements for the coarse (k,q) grid but the matrix elements in real space (after Wannier rotations). If you want the matrix elements on the (k,q) grid the easiest option is to use the 'prtgkk' input variable, and you can choose the fine (k,q) gri...

Hi Anindya,

You need the same number of processors and pools between the nscf and epw calculation.

Carla

Thank you for the useful link Vahid. Anindya, the phonons are unrelated to the wannierization of the band structure. You might need to redo the phonon calculation on a denser grid, but that would be in order to better converge your electron-phonon quantities. For now you can focus on obtaining a sat...

Hi Anindya,

The phonon calculation can be run with any number of cpus and pools you'd like, EPW will only read the saved files which are invariant.

Carla

Hi,

It is difficult to identify the possible cause without any additional information, such as the input file. Is there no error file too?
Also, have you been able to run some of the examples / tutorial successfully?

Best
Carla