[QE-users] Electron-phonon-wannier

[Timon Moško]

Dear espresso community,

recently I have been trying to calculate superconductive gap of NbSe2 using EPIq code. I do encounter problem while triyng to calculate electron-phonon-coupling matrix elements. I do follow strategy presented in example (https://the-epiq-team.gitlab.io/epiq-site/docs/tutorials/mos2/).
Used software - qe 7.2. I also attach the basic structure of my calculation and I do work with nonmagnetic SOC calculation.

I do struggle with multiple issues. The first one is the need to work with localized Wannier basis - according to the EPIq tutorial I should use in ph.x calculation of el-ph matrix elements flags:

electron_phonon='Wannier',
  dvscf_star%open=.true.,
  dvscf_star%basis= "cartesian",
  fildvscf='dvscf',
  dvscf_star%dir='./../2.phonon/Rotated_DVSCF'

However, I am struggling to find reasonable documentation for ph.x regarding 'Wannier' option for el-ph calculation. If there is some literature, please notify me .

In my case the problem emerges in this particular step, when I do possess wannierized electronic wavefunctions (./1.Wannier) and phonon modes (./2.phonon/ and rotated dvscf ./2.phonon/Rotated_DVSCF/) separately saved in two distinct folders. When I try to run ph.x el-phon calc (./3.Elph, with coppied dynamical matrices from from phonon calc) it seems to start writing dvscf files to electronic outdir - which I take to be folder ./1.Wannier (then it stores to ./Wannier/_ph0/), however, these files exists, but thety are empty and error occures:

   Error in routine davcio (90334):
     error reading file "/home/mosko/local/NbSe2_calc_with_epiq/3.Elph/../1.Wannier/_ph0/NbSe2.dvscf1_1"

If there is any way how to resolve this issue, please notify me.
Best
Timon


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