[Pw_forum] Re: Different Gamma factors for Q-points in the same star

[Eyvaz Isaev]

Dear Stefano, 

I am quite agree with your comment, but I suggested
(and hopefully it is) that the symmetrization is done
correctly in the code.  As you know the gamma
approximately is a sum of production of two delta
functions, connecting two parts of the Fermi surface,
and is believed to converge slowly wrt number of
k-sampling. That is why I suggested the use of  more
k-points.

Bests,
Eyvaz.

--- Stefano Baroni <baroni at sissa.it> wrote:

> Andrea, Eyvaz: I know nothing about the way the
> Eliashberg function  
> is calculated in Quantum ESPRESSO, but symmetry
> issues have (should  have) little (if anything) to
do > with k-point grids,  cutoff, and the  like. What
I 
> mean is that if  symmetrization is well implemented 
> (and   well understood by those who use the code) an
> inadequate cutoff and/  or k-point grid may well
give > inaccurate results,  but these results  
> should be the same (to _very_ high accuracy) whether
> calculated by restricting the BZ sampling to the 
> irreducible wedge (and properly  
> symmetrizing the result), or by the extending the
> sum to the full BZ.  
> Sorry for not being more helpful than this - Stefano
 

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