[QE-users] how to choose properly the parameters value of nq1, nq2 nq3 in the ph.x inputfile.

[Marcelo Falcão de Oliveira]

Dear Yang Gang,

   I am learning QE but I would proceed like this:
https://docs.google.com/document/d/1rA9VMpg_cQrmGpTiAalpF6J4LEIzDU2MrbSXNosxNI0/edit?usp=sharing
   I hope it helps.

Best regards,

Em qui., 27 de jan. de 2022 às 09:23, Gang Yang <gang.yang at ec-lyon.fr>
escreveu:

> Dear QE experts:
> I am doing phonon dynamics calculation. I want to obtain the second force
> constants using QE ph.x and q2r.x module. For the ph.x calculation, how to
> choose properly the parameters value of nq1,nq2 nq3 in the ph.x inputfiles.
> As you know, the parameters nq1,nq2,nq3 determine the number of outputfile
> dyn. I saw someone using nq1=2,nq2=2, nq3=2. or nq1=8,nq2=8,nq3=8. et al .
> if the paramter nq1,nq2 nq3 is too large, the calculation time is too long.
> if the parermeters nq1,nq2, nq3 is too small, I don't konw whether it will
> affect the precision of second force constants. in addtion, i also found
> the some specical nq1,nq2,nq3 value are not allowed for asymmetric
> structure.  therefore, my question is if I want to obtain a reasonable
> second force constants using q2r.x,  how I can choose the parameters value
> of nq1,nq2 nq3 when I using ph.x calculation in 10 atom primitive cell?
> Thank you very much.
> have a good day.
>
> Yang Gang
> Institut des Nanotechnologies de Lyon (INL) - UMR5270
> Ecole Centrale de Lyon
> 36, Avenue Guy de Collongue
> 69 134 Ecully Cedex
> Tél.: +33 (0)7 64 83 01 70
>
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Marcelo Falcão de Oliveira
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