[QE-users] mechanical stability under pressure from phonons

[Nicola Marzari]

I think what Grimvall is saying is that there has been no rigorous 
discussion before, but in their review they make this discussion, and 
show how the stability condition for phonons does not need any 
correction - the material collapses at the pressure where the phonon 
dispersions calculated at the corresponding volume go negative. Anyhow, 
they cite a few papers and their follow-up corrections.

nic


On 11/01/2021 11:04, Uri Argaman wrote:
> Hi all
> In the literature the mechanical stability condition using elastic 
> constants includes explicitly the pressure:
> In cubic symmetry, for example:
> C11 + 2*C12 +P>0;
> C44 +P>0;
> C11 + C12 + 2*P>0;
> from: Grimvall et al. REVIEWS OF MODERN PHYSICS, VOLUME 84,  2012
> In this paper, they write: " There seems to be no rigorous discussion 
> of this point in papers that have presented ab initio calculations of 
> phonon dispersion curves under pressure,..."
> The stability condition from phonons: omega>0 for all modes. It seems 
> that it is not equivalent, because the phonon condition is at 
> constant volume. Is it known what is the condition at constant pressure?
> Than you very much
> Uri Argaman
> Ben-Gurion University of the Negev
> Israel
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20210111/8c3cae16/attachment.html>