[Pw_forum] Relax structure after getting the cell relaxation result

[Lorenzo Paulatto]

On Wed, 14 Jan 2009 12:01:08 +0100, loc duong ding <mambom1902 at yahoo.com> wrote:
> I relax the cell of structure. After that, I use
> this result to relax ion positions. The input file for cell relaxation
> and ion relax is the same (only change 'vc-relax' to 'relax').

As far as I know, vc-relax relaxes the atomic positions as well, unless you specify ion_dynamic='none', which is not possible with bfgs.

> I don't understand why the pressures in two case are different.

They are zero in both case, where zero means "less than the convergence threshold".

I cannot be sure that when you are saying "I use this result" you are actually doing the right thing, but if you do then your 2 calculations are the same, and will give you the same results, inside the convergence threshold.


regards


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