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

[mohnish pandey]

Yea dear Linh, I have used the converged cell parameter from vc-relax
calculation for scf run,

Thnaks,
mohnish

On Sun, Apr 18, 2010 at 8:33 PM, Ngoc Linh Nguyen <nnlinh at sissa.it> wrote:

>
> > Dear Hanyu !
> >                      Thanks for your reply. As you now the default value
> > for
> > the pressure in PWSCF is 0.5.
>
> This value should be 0.0 as the default value (see in input PW website)
>
> > 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,
>
> Before doing scf calculations, have you changed the cell-parameters in scf
> input file as same as the converged cell-parameters from vc-relax?
>
> Best regards,
>
> Linh
>
>
>
> >
> > 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
> >> > -----------------------------------------------------------------
> >> >
> >> > _______________________________________________
> >> > Pw_forum mailing list
> >> > 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
> > -----------------------------------------------------------------
> > _______________________________________________
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://www.democritos.it/mailman/listinfo/pw_forum
> >
>
>
> -----------------------------------------------------
>  Nguyen Ngoc Linh, PhD Student
>  c/o:   SISSA & CNR-INFM Democritos,
>        via Beirut 2-4, 34014 Trieste (Italy)
>  email: nnlinh at sissa.it
>  phone: +39 04 03787 319
>  skype: ngoclinh84phys
> -----------------------------------------------------
> "The physics is theoretical but the fun is real"
>
>
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-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey
Y6927262,4th Year dual degree student,
Department of Chemical Engineering,
IIT KANPUR
09235721300
-----------------------------------------------------------------
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