[Pw_forum] Question about K-points

[Duy Le]

Dear Bipul,
I haven't done such kind of calculation. However, when reading your
question, there are couple of questions that may help you:

1. Did you perform the STRUCTURE convergence test for K-point mesh and/or
energy cutoff?
2. Did you use the relaxed equilibrium structure which was obtained by using
10x10x10 mesh and 32Ry cutoff to perform 14x14x14 mesh and 38Ry cutoff
phonon calculation?
3. How about the forces acting on the atoms in 2 cases? Are they too
different?

Hope those help!

-------------------------------------------------
Duy Le
PhD Student.
University of Central Florida.

On Sun, Aug 23, 2009 at 12:46 PM, Bipul Rakshit <bipulrr at gmail.com> wrote:

> Dear Pwscf users,
> I have a question about phonon calculation.
> I am doing phonon of K2S (antifluorite structure), using 10x10x10
> k-points mesh. In that calculations i find -ve frequencies.
>
> But then on increasing the mesh 14x14x14 and also the kinetic energy
> cutoff from 32 to 38 Ry, now i am getting all the +ve freq.
>
> Can you please tell me the reason or give me some reference, so that
> by reading that i can understand the things.
>
> regards
> --
> Bipul Rakshit
> Research Fellow,
> S N Bose Centre for Basic Sciences,
> Salt Lake,
> Kolkata 700 098
> India
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