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
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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
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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
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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
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
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