[Pw_forum] problem releated to calculating elastic constants

[Eyvaz Isaev]

Dear Premlata,






--- On Fri, 8/8/08, premlata pandit <lataprem29 at gmail.com> wrote:

> the experimental lattice constant of Li2S is 10.7867 a.u.
> and my calculated equlibrium lattice constant is 10.375
> a.u. by using LDA pseudopotential in pwscf calculation.
> can i use this lattice canstant to calculating  elastic
> constants?
>

The difference is around 4%, so, you can use it. Even you can use any lattice parameter for this purpose, the main question is what you expect. If you like compare with experiment, most likely calculated elastic constants will be larger than experimental ones. Commonly accepted practice is the use of experimental lattice parameter. But, for sure, you have to test pseudopotentials you apply.

Bests,
Eyvaz.

 
> -- 
> Premlata Pandit
> Bhopal (MP)


-------------------------------------------------------------------
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