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["Anglade Pierre-Matthieu" <anglade@gmail.com>]

Hi,

You mentioned keeping ecutsm constant between the two runs but what
about dilatmx ?
Did you tried the second run with a ecut2=ecut1*dilatmx**2 ?

regards

PMA

On Sat, Oct 11, 2008 at 5:56 PM, Josef Zwanziger <jzwanzig@dal.ca> wrote:
> Dear Colleagues,
> I've noticed this behavior in the past and never really understood it. I 
> would
> really appreciate an explanation from someone.
>
> When I optimize a cell with optcell = 1 or 2, and dilatmx = 1.1 and ecutsm 
> /= 0
> as required, I find typically that the cell optimizes nicely and the final
> computed pressure is very small, of course determined by whatever value I 
> set
> tolmxf to. Then, if I cut and paste the new acell and xred and rprim, and 
> do a
> normal ground state SCF run with the same convergence level (using either
> toldff or tolvrs), the computed final pressure is usually several orders of
> magnitude larger than the final value achieved in the optimization run. For
> example, if I choose really easy case like Si, I can optimize it to a 
> computed
> final pressure of 1E-4 GPa, and then those cell parameters in an SCF
> calculation will give a pressure of 1E-2. This gets worse in big cells, 
> where I
> might optimize to 1E-2 and then the SCF run gives 1 GPa. Why does this 
> happen?
> It seems to be independent of the value of ecutsm, and also I am running at 
> a
> pretty dense kpt set (kptrlen = 80). Any comments?
>
> thanks,
> Joe Zwanziger
>



-- 
Pierre-Matthieu Anglade