[Pw_forum] Is it possible to separate the phonon calculation from the el-ph calculation and use the GRID technique for phonons?

[Thomas Brumme]

Dear all,

my question is already given in the subject, but I want to
elaborate on it a little bit more. I have big system of 14 atoms
and thus 42 representations. Unfortunately, it is not possible
to use the image parallelization when doing an el-ph coupling
calculation. However, as 42 representations need quite a lot of
time, I run into the time limit of our HPC (just 24h) and always
need to restart calculations for the different q points.

I would like to know if it is possible to use the GRID parallelization
with el-ph and how to setup it properly.
I now tried a couple of hours and also searched the mail archive
for help, but maybe I used the wrong search terms!?

Calculating the phonons on a grid is in fact pretty easy and I
have no problems with that. I thought that I could maybe calculate
the phonons on a grid, then (or at the same time?) also calculate
the dvscf and then start the el-ph calculation with trans=.false.
but it is always complaining about something, mostly about
errors while reading the dvscf file...

Following the 1. grid example I calculated the phonons (I try at
the moment with simple Al) for different q points and
representations. Then - I thought - it would be enough to set
the fildvscf to something once I make the finale calculation to
collect the phonon results. But then I get problems. It seems
the code does not use/recalculate the density. The charge density
files in the iq subfolders of _ph0 were empty. So I copied them
from the grid subdirectories to the iq subfolders into the _ph0 dir.
Now, it seems, that the code is correctly calculating also the
dvscf files. Yet, if I now start the el-ph calculation the code
complains about errors in the dvscf file...

I could also provide the changed bash script I used to do all
these steps but I think it won't be very helpful.

If anyone has an idea how to use the grid parallelization for
a phonon calculation with a subsequent el-ph calculation, I
would be very grateful for help.

Thomas


-- 
Dr. rer. nat. Thomas Brumme
Max Planck Institute for the Structure and Dynamics of Matter
Luruper Chaussee 149
22761 Hamburg

Tel:  +49 (0)40 8998 6557

email: Thomas.Brumme at mpsd.mpg.de