[Pw_forum] Vc-relax again

[Paolo Giannozzi]

On Sat, 2014-03-29 at 20:26 +0300, Elio Physics wrote:

>  Professor Paolo G. gave me a link for this problem.. I understood
> that I need  to  increase the  cutoff kinetic energy 

did you also understand that you need first of all to check that the 
two systems you are comparing are the same?

> which I did and I realized that the pressure goes down but to -6;
> however the total force is still 0.4! 
> 
> 
> (1) Anyone knows how to solve this problem.
> 
> 
> I have run the calculation again wih ibrav=0 instead of ibrav=6 and
> the crystal axes were:
> 
> 
>               a(1) =   (   0.492694   0.853319   0.000001 )
>                a(2) = (   0.492685  -0.853314  -0.000001 )
>                a(3) = (   0.000001   0.000004   4.274389 )
> 
> 
> The pressure was -0.02 and the total force was 0.001 which was fine in
> both scf and vc-relax. However when I redid an scf calculation with
> ibrav=6 with c/a =4.274389 (which I read from the ibrav=0 calculation
> with the same atomic positions of the "ibrav=0" calculation), I still
> got P =-16 and total force=0.4.  I was trying to convert the ibrav=0
> input to ibrav=6..did I do anything wrong?
> 
> 
> 
> 
> Any help would be appreciated 
> 
> 
> Thanks
> 
> 
> Elio Nahdan
> 
> 
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-- 
Paolo Giannozzi, Dept. Chemistry&Physics&Environment, 
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222