is it possble to apply external pressure

Dear All;

I want to optimize the cell lattice under high pressure, is it possible in elk? I searched the manual by key words "stress" and "pressure", cannot find .....

Thanks

supermarche - 2015-01-09

Dear siewHy,

as far as I know, this feature is not yet implemented. One has to compare enthalpies (includes a pV term) instead of total energies in the case of non-zero pressure.

You can imitate the fixed pressure constraint by setting the volume constraint (latvopt=2). The deviation from from fixed pressure should grow with the size of the basis.

Best Regards,
Marc

Last edit: supermarche 2015-01-09

Brice KENGNI ZANGUIM - 2020-02-25

Hello,
So it is not yet possible to apply a pressure in the lattice or impose a stress tensor during calculation ! !

Dear siewHy, dear Brice,

Applying a pressure can be imitated via scale.
It is useful to know the experimental lattice size under pressure.
Then, just use that value in the calculations.

Following supermarche's answer, latvopt=2 will allow geometry optimization with fixed volume, effectively keeping the cell "under pressure".

Finally, the cell is treated as infinite, while the pressure acts on a boundary.
Thus, I am not sure if it is possible to "apply pressure" is a periodic cell calculation in a way other than the scale.

Regards.
Andrew

https://sourceforge.net/p/elk/discussion/897820/thread/fbb472e5/