[Pw_forum] qe_6.0 nr fixed in q_gen subroutine

[Paolo Giannozzi]

I think 4x4x4 is not directly related to the q-point grid, but to the
maximum size of the supercell (if you want to build a supercell with force
constants computed in the unit cell. It was used once upon a time in
GaAs/AlAs heterostructure, I think)

Paolo

On Tue, Nov 15, 2016 at 9:00 AM, Antoine JAY <antoine.jay at polytechnique.edu>
wrote:

> Dear community and developers,
>
> Looking at the code of qe_6.0
>
> I am wondering why in PHonon/PH/matdyn.f90
> subroutine q_gen
>
> the values nr1, nr2 and nr4 are fixed to be 4:
> INTEGER, PARAMETER:: nr1=4, nr2=4, nr3=4
>
> whereas they should be fixed as nr1=nq1, nr2=nq2, and nr3=nq3.
> as done by the first call of read_ifc_param(nr1, nr2, nr3).
>
> Is there a physical meaning?
> Is this subroutine right if someone don't whant a 4^3 q-mesh?
>
> Antoine Jay
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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