[Wien] problem of structure optimization by minimizing the forces

[L. D. Marks]

The referee is somewhat correct, and somewhat incorrect. If you use the 
PORT option you are minimizing the energy, not minimizing the forces. 
Minimizing the magnitude of the forces may find a minimum, but it may also 
find a saddle point -- hence the PORT option does NOT minimize the 
magnitude of the forces in each step and the forces can increase. If you, 
by hand, minimized the magnitude of the forces, go back and check it 
properly; the minimizer underneath the PORT option (dn2g) has a large 
number of clever checks and clever coding (it was written some years ago 
by some of the biggest names in optimization) to try and make it as safe 
as possible.

On Sun, 11 Jun 2006, Bing Zhou wrote:

> Dear All,
>
> After I got the optimized crystal structure by minimizing the forces at
> the nuclei using WIEN2k, the peer reviewer made such a comment as:
>
> "hopefully you did not change positions until the forces reach a minimum
> (because forces could also be negative!!!). You minimized the magnitude
> of the forces!"
>
> So anything I did is wrong? if yes, how can I remedy it?
>
> Any rely is highly appreciated!
>
>
>
> Bing Zhou
> Dept. of Geol. Sc.
> The Univ. of Manitoba
> Canada R3T 2N2
> Tel: (204)474-8395
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>

Note: if you have an old email address for me, please note that "nwu" has
been changed to "northwestern".
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Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2225 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
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