[Pw_forum] vc-relax bug?

[cesards at msi.umn.edu]

Hi Javier,

After your first cell optimization, try starting again from scratch
using the final configuration of the previous calculation. If the problem
persists, increase the cutoff energies.

Good luck.

Cesar R.S. da Silva

>
> Message: 10
> Date: Wed, 4 Apr 2007 17:31:23 +0200
> From: "Javier Antonio Montoya" <j.antonio.montoya at gmail.com>
> To: pw_forum at pwscf.org
> Subject: [Pw_forum] vc-relax bug?
> Reply-To: pw_forum at pwscf.org
>
> ------=_Part_26133_24163750.1175700683893
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> Content-Transfer-Encoding: 7bit
> Content-Disposition: inline
>
> Hello dear all,
>
> In recent days I have been trying to get a triclinic cell to have a
> diagonal
> stress by using vc-relax. The pw.x program reads data in the correct way,
> calculates the right starting volume for the cell given as input and also
> seems to do right the first electronic minimization but, as soon as the
> Wentzcovitch Damped Cell-Dynamics Minimization starts, it gives cell
> parameters and ion positions that are not consistent with the energies and
> stress that it prints (i.e. if you take those cells and ions to an
> independent scf run the final energy and stress differ from the ones in
> the
> vc-output) the problem is that in the end, when I get a nice diagonal
> stress
> after 60 or more dynamic steps, the difference between the reported energy
> in the vc-output and the energy of the system that you get with the cell
> and
> ion parameters shown is of almost 1 Ry and the pressures differ by more
> than
> 10GPa. Any idea? by the way the ph.x complain and doesn't get anything
> from
> such restart files.
> The output files are huge for sending by e-mail because my system is 72
> atoms big, but I can provide them.
>
> cheers,
>
> JAvier.
>