[Pw_forum] elastic constant and bulk modulus

[Eyvaz Isaev]

Dear Sezgin,

You should find the same question on the forum.
Nevertheless, you can calculate elastic constants and bulk modulus applying strains according to original paper of Mike Mehl et al., Phys.Rev.B 41, 10311 for cubic and tetragonal lattices.
For hexagonal lattices see a paper of R.Cohen on elastic constants of iron published also in PRB. Anyway, search PRB for straines for different lattices.

Of course, you could calculate elastic constants as a slope of phonon dispersion relations in the long-wave approximation i.e. for q-points near Gamma point, but this way seems to be more expensive, as the derivative is quite sensitive to details of phonon calculations and one needs converged phonon calculations for this purpose. 

And I am not sure whether elastic constants calculations in DFPT according to Hamann et al. is implemented. At least, I never heard about this opportunity.

For  bulk modulus only calculations just calculate E(V) or (E(a) for cubic lattices) and then use ev.x from /tools directory to find B.

Hope this hels.

Bests,
Eyvaz.

-------------------------------------------------------------------
Prof. Eyvaz Isaev, 
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, 
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden 
Condensed Matter Theory Group, Uppsala University, Sweden 
Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com


--- On Mon, 1/26/09, sezginaydin at gazi.edu.tr <sezginaydin at gazi.edu.tr> wrote:

> From: sezginaydin at gazi.edu.tr <sezginaydin at gazi.edu.tr>
> Subject: [Pw_forum] elastic constant and bulk modulus
> To: pw_forum at pwscf.org
> Date: Monday, January 26, 2009, 11:12 AM
> Dear PWScf users,
> how can I calculate elastic constant and bulk modulus by
> using PWScf package
> 
> thanks for your help
> -sezgin
> 
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