[Wien] mini with constrains

L. D. Marks L-marks at northwestern.edu
Wed Mar 23 16:00:53 CET 2005

A good question, with a slightly complicated answer. If two (or more)
atoms are linked by symmetry relationships or something else, this should
(with some caveats about numerical accuracy) also be there in the forces
and the second derivative matrix. Even though you may have N positions
and the full matrix may be NxN variables, there will only be M independent
positions and a smaller MxM effective matrix. The time for a minimization
should therefore scale something like M**alpha where alpha is some
nebulous parameter between 1-2.

In principle one can insert a matrix variable conversion into mini to
convert from one set of variables to another which might be useful in some
special cases, but for general problems would not be useful.

On Wed, 23 Mar 2005, Gilles Hug wrote:

> Ok very good so I proceed like that.
> The real question was what happens if I have for example two of such
> atoms?
> Does mini search in a 4 dimensions space or in a 2 dimensions space?
> Even though the result will always be the same the efficiency might be
> different.
> Cheers,
> Gilles

Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60201, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L - marks @ northwestern . edu

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