[Pw_forum] total force and number of k-points

[Elie Moujaes]

Professor Giannozzi,
Thanks a lot for your reply.
Elie

> From: giannozz at democritos.it
> Date: Fri, 2 Sep 2011 22:55:25 +0200
> To: pw_forum at pwscf.org
> Subject: Re: [Pw_forum] total force and number of k-points
> 
> 
> On Sep 2, 2011, at 15:54 , Elie Moujaes wrote:
> 
> > I have a simple question: does the total force acting
> > on a system depend on the number of k-points  used?
> 
> not sure what you mean by "total force", but forces on
> atoms depend upon the number of k-points, for sure
> 
> > That is in my scf calculation I am using a grid of 4x4x1
> > for my system whereas the grid must be denser if phonon
> > calculations are taking place I am using 8x8x1. Do I get
> > different total force acting on the system and does it mean
> > I have to relax the crystal twice one for an scf calculation
> > and another for  a phonon calculation?
> 
> in principle a system should be relaxed for the same set of
> parameters (cutoff, k-points) that are used in the subsequent
> phonon calculation. The difference might be small enough to
> be negligible, but this is something that should be checked.
> 
> P.
> ---
> Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
> 
> 
> 
> 
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