Geometry optimization for weakly bound systems (fwd)

[Dr. Martin Schuetz]

Answer to problem described by Dave Moore...

Dear Dave,

There exists a second optimizer in MOLPRO (which is undocumented and
still experimentel) which might be more adaequate for optimizing
weakly bound systems. It is described in CPL 303, 567 1999 and uses
force-weighted redundant coordinates. You can activate it with e.g.

...
optg;coord,cart;method,slrf;linesear,-1

optionally, you could try optg;coord,cart;method,slrfwh;linesear,-1
or optg;coord,cart;method,slrfwb;linesear,-1 (the latter two cases
use an additional forcefield (appropriate for hydrogen-bonded systems)
in the update or in the update and the selection of the nonredundant
coordinates, respectively. Again, this is still experimentel, but I used
it successfully for the optimization of water clusters of intermediate
size. Use cart. coordinates for the specification of the input geometry
and don't forget to supply the noorient keyword.

Hope that helps. Apart from that there is not much we can do without an
input.

Best
Martin


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Dr. Martin G. Schuetz                         Phone: 0049 (0)711-685-4397
University of Stuttgart                       Fax:   0049 (0)711-685-4442
Institute for Theoretical Chemistry
Pfaffenwaldring 55                            Room Nr: 8.161                
D-70569 Stuttgart                          
Email: schuetz at theochem.uni-stuttgart.de       
WWW  : http://www.theochem.uni-stuttgart.de/~schuetz/
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