[Pw_forum] a2Fq2r files - electron-phonon coupling

[Sridhar Sadasivam]

I found the same question already asked in this forum a few years back:
http://qe-forge.org/pipermail/pw_forum/2010-May/091560.html

Prof. Giannozzi, you had answered that they contain the electron-phonon
coupling matrix elements. But I still do not understand the format of these
files. I am actually interested in getting the raw coupling matrix elements
instead of the other outputs such as Eliashberg function or the lambda
values. So could you please explain the format of these files?

I also don't understand why the coupling matrix elements would depend on
broadening values. For example, if you look at the definition of the
electron-phonon coefficients in the link below (see Equation 1 in
Appendix), it does not have any delta functions. Only the line width (and
the Eliashberg function, lambda) have delta functions in them and hence
would depend on the choice of broadening parameter.

http://www.quantum-espresso.org/wp-content/uploads/Doc/ph_user_guide.pdf

I am very confused and I would really appreciate any sort of help. Thanks a
lot,
Sridhar
Purdue University


On Thu, Mar 13, 2014 at 10:53 AM, Sridhar Sadasivam <sridhu88 at gmail.com>wrote:

> Hello,
>
> I have a question about electron-phonon coupling in Quantum Espresso. When
> ph.x is run with electron-phonon coupling (la2F = .true.), it outputs a
> series of files a2Fq2r.* (* = 51-60). Could someone explain what exactly is
> contained in these files? Do they contain the electron-phonon coupling
> matrix elements?
>
> I did not find much information on this in the documentation. Thank you!
> Sridhar
> Purdue University
>
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