[Pw_forum] k grid points in the calculations of electron-phonon interaction coefficients

[Lorenzo Paulatto]

On 11/17/2013 05:16 AM, Caloma Trumica wrote:
> In the manual of calculating electron-phonon interaction coefficients:
> 
> http://www.quantum-espresso.org/wp-content/uploads/Doc/ph_user_guide/node9.html
> 
> Item 1 says that: "The latter MUST contain all [image: $ \bf k$] and [image:
> $ \bf k$] + [image: $ \bf q$] grid points used in the subsequent
> electron-phonon calculation"
> 

If I remember correctly, it's enough that an equivalent k+q+G point is
found; where G is a vector of the reciprocal lattice.

In order to guarantee this it's sufficient that the q point is one of
the k points and that the k point grid is centered around Gamma. In more
general terms, the q grid must be a subset of the k grid.

I.e. if your q grid is composed by n1 x n2 x n3 points the k-point grid
can be (n1*m1) x (n2*m2) x (n3*m3) where everything is integer.

bests


-- 
Dr. Lorenzo Paulatto
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