[Pw_forum] force

[Paolo Giannozzi]

On Aug 20, 2009, at 17:11 , ali kazempour wrote:

> I use vc-relax to optimize the lattice constant and also the  
> position for bulk.
> After I make supercell with these optimized value and run a scf  
> with similar
> value as bulk. But the force as I listed below for some atom is  
> relatively more
> than other

I see quite small forces. If you do a supercell, do not forget that  
you will not
get exactly the same values as for the original cell, unless the k- 
point grid
of the unit cell refolds into the k-point grid of the supercell

Paolo
---
Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222