Run Wannier90 and EPW separately.

[spguo]

Dear EPW,
I try to run Wannier90 and EPW separately. Unfortunately, I encounter the problem to save the prefix.ukk file. I check the codes and find that it is EPW not Wannier90 that could generate the file. However, the write_filukk subroutine is part of the EPW code and it needs inputs from pervious subroutine runs. Would you please tell me how to run the write_filukk subroutine separately, based on the Wannier90 outputs?
Thanks,
Cathy

[sponce]

Dear Cathy,

This is probably not so simple to do.
Why not simply running EPW which will call Wannier90 internally.

EPW supports most of w90 features.

You can always add w90 input variables inside the EPW input file by adding them through the "wdata(X)" keyword.

Best,
Samuel

[adenchfi]

Is there any update to this? Perhaps Wannier90's 'write_u_matrices' parameter serves this purpose?

In particular, we're looking at how feasible it could be to make an EPW-VASP interface (unless you already know of one).

[hlee]

Dear adenchfi:

I remember that I already gave you some guideline:
viewtopic.php?p=3237#p3237

This is not difficult to implement, but we don't have a plan to implement it since the users are likely to misuse this functionality; I already told you the following:

However, you should be VERY careful at the fact that you should use the SAME wavefunctions in constructing Wannier functions and evaluating the electron-phonon matrix elements. Otherwise, your results are totally meaningless due to the gauge inconsistency.

Regarding the EPW-VASP interface:

In particular, we're looking at how feasible it could be to make an EPW-VASP interface (unless you already know of one).

I don't know whether or not there is a EPW-VASP interface available, but I think that it is much more difficult to make the EPW-VASP interface than to implement the functionality for importing the relevant data from Wannier90.

Sincerely,

H. Lee

[adenchfi]

Thank you for the feedback H. Lee, I recalled your previous advice so my question I suppose was more about the VASP-EPW interface. I will communicate with my colleagues about the difficulty.

[fanchem]

I have modified the code in wannier90 a bit so that it could generate the *.ukk file needed for EPW. However, when running from EPW, cautions should be taken on the wavefunctions, e.g. you need to use the same *.save folder for EPW calculation as in independent wannier90 calculations.

The modified cold could be found at https://github.com/fanchen0121/home_wannier90 .
I used two more variables due to my laziness. One is "exclude", which is an integer, just the number of bands going to be excluded in the EPW calculations. For example, if you use "bands_skipped = 'exclude_bands = 1:8" in EPW calculations, then the new exclude tag should be 8. The other variable introduced is "alat", which is a real number, and can be obtained from scf or nscf calcualtions.

Best,
Fanchem