[Pw_forum] Trouble in phonon calculation

[Eyvaz Isaev]

Hi,

Probably, you should decrease the alpha_mix parameter
for phonon calculations inserting a new line and
specifying alpha_mix=your_choice (right after nscf
calculations for a given q-point). By default
alpha_mix=0.7 and for surface (supercell) calculations
it should be of order of 0.1 (at least, not 0.7).

Regards,
Eyvaz Isaev
  
--- "Hong, SamPyo" <likedew at phys.ksu.edu> wrote:
> Dear PWSCF users,
> I just want to get advices from your experiences.
> Now I'm trying to
> calculate phonons of a Ni slab.
> Only one of the modes won't converge. Number of its
> iteration is going
> beyond 100. Worst of all, even after 100 iterations,
>  |ddv_scf|^2 is
> more than 0.4E+8. The other modes usually converged
> within 6 or 7
> iterations. I don't get any error messages during
> the phonon
> calculation. Could any of you who have experience
> with phonon
> calculation with PWSCF advise me about this trouble?
> What could be the
> reason? Obviously the structure relaxation was done
> completely for
> phonon calculation. The residual forces in the slab
> are very low.
> 
> Just another question: Is there any way to know the
> frequencies of the
> already converged modes in PWSCF? Or is it
> impossible?
> 
> Thanks a lot!
> 
> Sampyo
> 
> 


__________________________________
Do you Yahoo!?
Yahoo! SiteBuilder - Free, easy-to-use web site design software
http://sitebuilder.yahoo.com