[Pw_forum] choosing ecutwfc through vc-rx

[Lorenzo Paulatto]

On Sun, May 31, 2009 04:52, Mehrnaz Anvari wrote:
>  1.If  I  want to achieve the equilibirium value of lattice paramrters
>  (such as a, c,...) is it possible to replace bulk modulues calculations
>  with vc-rx?

Yes, that's what it's made for. Anyway, it may be a good idea to compute
the bulk modulus anyway, in order to test your setupe and your
pseudopotentials.

>  2.when I use vc-rx for my material most of the time after 300 stpes the
>  stress becomes approximately zero(-0.6-0.6) but energy doesn't converge.

There is some error in you input, or you have bad pseudopopotential.
Probably you are using damped-dynamics that are not damped at all.

> Now I think it couldn't be true & I
> have to  optimize my ecutwfc during vc-rx calculation (Is it true?) what
> about k-point ,where could I optimize it?

Just take a reasonable configuration to test convergence and than relax to
fine-tune the parameters.

regards

-- 
Lorenzo Paulatto
SISSA  &  DEMOCRITOS (Trieste)
phone: +39 040 3787 511
skype: paulatz
www:   http://people.sissa.it/~paulatto/



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