[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&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222