[Pw_forum] 3 questions about elph file of Calculation of electron-phonon interaction coefficients

[Paolo Giannozzi]

On Saturday 16 April 2005 15:33, Liu Lei wrote:

> I just did calculation of electron-phonon interaction coefficients on
> MgB2 using GGA. [...]
> 1st question, which Gaussian Broadening value should be right?

in MgB2, calculating phonons and electron-phonon coefficients is the 
easy part; getting them right, i.e. converged, is the difficult part. Of
course, the important phonons and electron-phonon coefficients are 
by far the slowest to converge

Anyway: there are many published calculations on MgB2. You can
use those results to have an idea of what k-point grids and broadenings
are needed and to check your results. For sure, you need a lot of k-points.

Ten values of the gaussian broadening are reported in the evaluation 
of the double-grid because this helps you in locating a range of k-points 
and of broadenings that yield stable results. The code is in PH/elphon.f90 
and it is quite easy to understand and to modify. 

Paolo