[Pw_forum] phonon calculation for optimized geometry -one subtle confusion

[mohnish pandey]

Dear Hanyu !
                     Thanks for your reply. As you now the default value for
the pressure in PWSCF is 0.5. I am using that value as convergence threshold
but when I am doing scf calculation with the geometrical parameters value
obtained from the vc-relax calculation the pressure value is different from
vc-relax final run. And as you know pressure will effect the phonon
dispresion relation..Can you please give me any suggestion,

Thanks alot,
MOHNISH

On Sun, Apr 18, 2010 at 3:00 PM, Hanyu <ouuing at gmail.com> wrote:

> dear mohnish :
> I think you should check it carefully again. I don't think it should
> be happen. In fact, the stress of scf and vc-relax should be the same.
> but if the stress is not the hydrostatic pressure, the result is not
> be believed. you have to relax the structure until the stress of the
> phase is what you want.
>
> best regards.
>
> Hanyu
>
> On Sun, Apr 18, 2010 at 11:16 AM, mohnish pandey <mohnish.iitk at gmail.com>
> wrote:
> > Dear users,
> >                   I want to do phonon calculation for some structures,
> but
> > after geometry optimization when I am using optimized geometry parameters
> > for scf calculation there is difference in stress of scf calculation and
> > vc-relax calculation which is changing phonon dispersion. Can anybody
> please
> > tell me if there is any option to use the data of relax or vc-relax
> > calculation for phonon dispersion.. Or can I doing phonon calculation
> along
> > with relax or vc-relax calculation.?
> > Thanks a lot in advance,
> >
> > --
> > Regards,
> > MOHNISH,
> > -----------------------------------------------------------------
> > Mohnish Pandey
> > Y6927262,4th Year dual degree student,
> > Department of Chemical Engineering,
> > IIT KANPUR
> > 09235721300
> > -----------------------------------------------------------------
> >
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> > Pw_forum at pwscf.org
> > http://www.democritos.it/mailman/listinfo/pw_forum
> >
> >
>
>
>
> --
> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=**=-=**=-=**=-=*=-=*=-=*=-=*=-=*=-
>  Hanyu Liu(刘寒雨),
>  MS.
>  State key  Laboratory of Superhard Materials, Jilin University, China
>  Email: liuhanyu08 at mails.jlu.edu.cn    ouuing at gmail.com
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>



-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey
Y6927262,4th Year dual degree student,
Department of Chemical Engineering,
IIT KANPUR
09235721300
-----------------------------------------------------------------
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