[Wien] Minimization

[Laurence Marks]

On 12/26/06, NAJMEH SOLTANI <naj23s at yahoo.com> wrote:
> Dear Laurence Marks,
> Thanks for your answer
> first I should say that I calculate Optical and electrical properties, so
> according what I read these properties are not related to forces, so I
> should not continue to minimize.Am I right?

I expect that these properties are not too sensitive to the positions
of the atoms at the level of forces of 1-2 mRyd/au. However, checking
this is YOUR job!

> Second I read in the mailing list which says" port in case.inM converges the
> energy so, the fluctuation of forces is not important."
> If it is correct  and port works with energy why do we perform the scf sycle
> with force convergance and minimize with force  and check the forces in
> case.scf according to TiO2 in UG?

A single scf cycle with force convergence will give you the forces
only for a single set of atomic positions. The minimizer uses both the
forces and energy to control how it moves the atoms, but strictly
speaking minimizes the energy. There are cases, particularly with
approximate calculations, where the forces may not be completely
consistent with the energy.

> Regards,
> Najmeh Soltani
>
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-- 
Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60208, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L-marks at northwestern dot edu
http://www.numis.northwestern.edu