[Pw_forum] phonon instability

[bhabya sahoo]

no i have calculated correctly because the convergence is good with higher k
points
second is that i have tested zns,wc,NiAs phase none of them have less
enthalpy at 130 gpa
other thing is that it is stable at above 250 gpa


On Wed, Aug 24, 2011 at 7:38 PM, Mike Mehl <Michael.Mehl at nrl.navy.mil>wrote:

> If the B1 structure is unstable with respect to the B2 structure above
> 130 GPa, but the B2 structure is dynamically unstable at and above 130
> GPa, there are two possible conclusions:
>
> 1) The phonons for the B2 structure were not calculated accurately, or
>
> 2) There is a competing structure that is lower in enthalpy than B1 or
> B2 at 130 GPa
>
> Without more information, no one can judge which conclusion is correct,
> suggest remedies for 1), or possible structure for 2).
>
>
> On 08/23/2011 02:40 PM, bhabya sahoo wrote:
> > sir
> > i am calculating the phase transition of some carbides
> > the transition from B1 to B2 transition occures at 130 gpa by enthalpy
> > compparison
> > but i am able to find phonon instability at 130 gpa for B1 structure
> > but at the same time i am not able to find the dyanamic stability of B2
> > phase
> > but it occures high pressure (more than130 gpa )
> > is there any explanation for this ?
> >
> > is there any relation of thermodyanamical unstability
> > and dyanamical unstability simultaneously?
> >
> >
> > answers are highly appriceted with some reson
> >
> >
> >
> >
> >
> >
> >
> >
> > Bd sahoo
> > reserch scholar
> > barc mumbai
> >
> >
> >
> > _______________________________________________
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://www.democritos.it/mailman/listinfo/pw_forum
>
>
> --
> Michael J. Mehl
> Head, Center for Computational Materials Science
> Naval Research Laboratory Code 6390
> Washington DC
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20110824/9903e9cd/attachment.html>