[Pw_forum] how to consider the "dt" flag during vc-relax

[Chaohao Hu]

Dear Cesar,

Thank you for your reply. According to your suggestion, I change "dt" and
conv_thr to 80 and 1.D-10, the convergence is not improved, although the
calculation is running.  The  calculated  total  force  and  stress  is
given here as a attachment because it is too long. As you can see from this
file, the final cell parameters is changed  largely, which also affects the
k-points meshing during my calculation. Another point added here is that my
systems only contain some light elements like H, Li. How to further optimize
these parameters?

Regards,
C.H.

On 10/23/07, Cesar R.S. da Silva <cesards at msi.umn.edu> wrote:
>
> Dear Chao,
>
> Your dt setting should work OK. wmass could be reduced to somthing like
> 0.002, provided atomic masses are all set to the average mass (amu), but
> your value is not that bad. The only thing I think could produce
> convergence problems is your conv_thr. Try conv_thr = 1e-9. Variable cell
> requires precise stress calculation, and a more stringent convergence
> criteria for the SCF cycle is required.
>
> Cesar.
>
>
-- 
============================
C.H. Hu
Postdoctoral fellow
Chimie et Physico-Chimie appliquees
Institut Francais du Petrole (IFP)
Rueil-Malmaison, France
E_mail: chaohao.mse at gmail.com
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