[CPMD-list] problems with point group recognition and symmetrisation of coordinates

[Christian Tuma]

Hello,

On Fri, Mar 19, 2004 at 01:55:01PM +0100, Juerg Hutter wrote:
> C   - Positioning of the molecule:
> C            z-axis   is the principal axis
> C            x-axis   is the two-fold axis
> C            xz-plane is the sigma-v plane
> C            xy-plane is the sigma-h or the Cs symmetry plane
> C            origin   is the center of inversion

These conditions cannot be fulfilled completely in the case of the Td-group.
Here the three C2-axes are orthogonal to each other, and the (four) principal
axes (C3) are not orthogonal to any of the C2-axes.
For some reason, however, using one of my two examples (the one with the z-axis
corresponding to a C2-axis and the xz-plane as a mirror-plane, see previous
posting), the point group Td was recognised, but, the symmetrisation failed.

Some years ago I used CPMD 3.0h (!) for a molecule in C3v-symmetry, at that
time the symmetrisation worked well (at least for this case of C3v). Using
the same input and CPMD 3.7.2 the symmetrisation fails. This might be an
indication that at least the problem of the symmetrisation of coordinates
could be related to a bug which might have arisen in the development towards
version 3.7.2.

> It's still possible that there are some bugs for certain
> point groups.

Yes, e.g. systems in D3d are not recognised as such. I carefully tested
it according to the rules you mentioned. At least C3v was working here,
maybe the problems are connected to the three C2-axes in the xy-plane.

Is there a chance that these problems might get fixed in the next CPMD release?

With best regards,
Christian Tuma.

-- 
Christian Tuma             Humboldt-Universitaet Berlin
ct at chemie.hu-berlin.de     Arbeitsgruppe Quantenchemie (Prof. Sauer)
phone: +49-30-20937140     Brook-Taylor-Str. 2, 12489 Berlin, GERMANY
fax:   +49-30-20937136     http://www.chemie.hu-berlin.de/ag_sauer