Polaron: Error in getting the polaron wave function in real space

[Qiaolin]

Dear all

I do calculate the polaron via epw 5.7 with input file under the "Hands-on tutorial: Polarons" at the link below: https://epw2023.dryfta.com/74-schedule, however, the procedure gets trouble when I try to get the polaron wave function in real space (contained in file 'psir_plrn.xsf'). By checking the file 'EPW5.7/src/polaron.f90', I find that the problem stems from the 'SUBROUTINE write_real_space_wavefuntion', which emphasizes that it is necessary to read cube files for the real-space Wannier funtion Wm(r). However, how can I get these cube files?

while running the epw calculations to get the polaron wave function after successfully completing phonon, scf, nscf and polaron-scf calculations, I am getting the following information in the outfile of epw calculation:
```
===================================================================
Use the band from 1 to 3 total 3
Including bands: 1 2 3
Use the band from 1 to 3 total 3 in saving g
Gathering eigenvalues of 3 bands and 200 k points
The band extremes are at band 3
Fermi Energy is 0.7269236 (eV) located at kpoint 92 0.000 0.000 0.000 band 3
Allocating arrays and open files.
End of plrn_prepare
Interpolating the Ank at given k-point set....
Start of interpolation of electronic band structure.
The largest Amp 1 0 0 0
Interpolating the Bqu at given q-point set....
Calculating the real-space distribution of polaron wavefunction....
```

The program seems to terminate abnormally because there are no cube files for the real-space Wannier function Wm(r). How can I get these cube files?

Best,
Qiaolin

[jlb]

Dear Qiaolin,

That is correct; In order to write the polaron wave function in real space, the Wannier functions in .cube file format are required.

These can be written with EPW by setting the input variable wannier_plot = .true. (see https://docs.epw-code.org/doc/Inputs.html#wannier-plot and related variables).

For example, in the hands-on tutorial that you mention, this variable is set to true in lif.epw1.in, and you should see the lif_*.cube files written as output.

Best,
Jon

[Qiaolin]

Dear Jon

Thank you very much for your reply. I have successfully resolved the issue based on your suggestions.

thanks again,
Qiaolin