[Pw_forum] vc-relax

[Paolo Giannozzi]

On Aug 28, 2008, at 3:52 , alan chen wrote:

> I try to relax the z-axis of STO while its x- and y-axis are fixed  
> (i.e. relax STO under strain). I use 'vc-relax' and cell_dofree=z.  
> The ion-dynamics is 'damp' and cell_dynamics is 'damp-w'. However I  
> found that this 'Wentzcovitch Damped Dynamics' always does 50  
> iterations and stops. But the strain along the z direction is not  
> necessarily the smallest after 50 iterations. Usually the z-strain  
> is smallest after some iterations (for example 30 iterations) then  
> it goes up.

this behavior is quite typical for damped dynamics that are not  
"damped" enough,
I think

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