[Pw_forum] Electron - phonon matrix element

[Subhodip Chatterjee]

Dear QE users,

How to extract the values of the two terms  and  of McMillan -
Hopfield expression from an electron - phonon coupling calculation? I'm
using QE-5.4.0.

I have seen related posts in the forum, but unable to figure out how to
proceed. I believe these are not printed in output files. So it would be a
great help if someone can guide me to obtain these two.

Best regards,
Subhodip

-- 
*Subhodip Chatterjee*

*Senior Research Fellow*

*Department of Chemistry*
*University of Calcutta*
*Kolkata, India*
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[Pw_forum] electron-phonon matrix element

[pourya]

Dear all

I would like to know whether the out put file with following format
elph.1.1.xml is electron-phonon matrix element or not.

Thanks in advance,
P.Ayria
Tohoku University Japan
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[Pw_forum] electron-phonon matrix element - relationship between npert and nu

[Lorenzo Paulatto]

On Mon, 19 Dec 2011 12:48:42 +0100, Paolo Giannozzi  
 wrote:
>> Can you please refer to the variables which store the basis for
>> atomic displacements ?

At the end of the phonon calculation, the phononic eigenvectors are  
printed at the end of the fildyn file.

During the phonon calculation the symmetry-dependent patterns are stored  
in the variable "u" from module "modes".

best regards


-- 
Lorenzo Paulatto IdR @ IMPMC/CNRS & Universit? Paris 6
phone: +33 (0)1 44275 084 / skype: paulatz
www:   http://www-int.impmc.upmc.fr/~paulatto/
mail:  23-24/4?16 Bo?te courrier 115, 4 place Jussieu 75252 Paris C?dex 05

[Pw_forum] electron-phonon matrix element - relationship between npert and nu

[Paolo Giannozzi]

On Dec 19, 2011, at 2:01 , Ajit Vallabhaneni wrote:

> Can you please refer to the variables which store the basis for  
> atomic displacements ?

?

---
Paolo Giannozzi, IOM-Democritos and University of Udine, Italy

"Nothing is impossible for the man who doesn't have to do it himself"

[Pw_forum] electron-phonon matrix element - relationship between npert and nu

[Paolo Giannozzi]

On Dec 16, 2011, at 17:50 , Hua Bao wrote:

> The electron-phonon matrix element is written in terms of ibnd,  
> jbnd, ik, ipert+imode0. (in elphon file) [...] However, I am still  
> having difficulty to project nirr/npert to a specific \nu.

you shouldn't need to project anything. Electron-phonon matrix  
elements have to
be symmetrized. The irrep basis is used for symmetrization. After  
symmetrization,
the electron-phonon matrix elements are expressed in the basis of atomic
displacements. Phonons are available in the basis of displacements as  
well.
So you can forget about irreps. Or at least, this is what I remember,  
in at least
one of the many possible ways to calculate electron-phonon  
coefficients. In the
current development version, there are three, plus one with an  
external code

P.
---
Paolo Giannozzi, Dept of Chemistry,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222

[Pw_forum] electron-phonon matrix element - relationship between npert and nu

[Ajit Vallabhaneni]

Dear Paolo,

  Can you please refer to the variables which store the basis for 
atomic displacements ? 


Thanks
AK

[Pw_forum] electron-phonon matrix element - relationship between npert and nu

[Hua Bao]

Dear Paolo and QE-users,

The electron-phonon matrix element is written in terms of ibnd, jbnd, ik,
ipert+imode0. (in elphon file)
Based on your discussion with Ajit, I realize that ipert is the number of
perturbations.

However, I am still having difficulty to project nirr/npert to a specific
\nu. It can be easily understand they are related, though.

For a phonon wave vector q, there are \nu phonon modes. These modes are
categorized into nirr irreducible representations, and each nirr has npert
perturbations? Can I assume one perturbation is a component of one phonon
pattern?

Would you please point out the relationship between npert and \nu?

Thanks,
Hua
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