[molpro-user] SAPT performance

[Tatiana Korona]

Dear Dr. Berger,

The fact that both monomers are the same is usually not important since 
calculations are performed in a dimer-centered basis set, so for most 
configurations of a complex there will be small differences in coefficients 
between monomers resulting from utilizing ghost orbitals. Only for a couple of 
very symmetric cases (e.g. if there is the center of inversion) the results 
(energies, SCF vectors etc.) of one monomer could be in principle copied for 
another monomer. This would require however writing a new part of the code and, 
as I said, will be of a very limited value. Maybe one could use looser 
thresholds for grids, DF etc., but I do not recommend this (maybe one of the 
DFT-SAPT authors will answer this issue more competently). The only thing that 
can be tried safely in your input is to restart KS for the second etc. distances 
from vectors $ca and $cb, respectively, saved from a previous distance in your 
loop.

Best wishes,

Tatiana

On Sun, 7 Nov 2010, Berger Raphael wrote:

> Dear Molpro-Users,
>
> I try to do some SAPT calcluations on a "relatively small" symmetric dimer. 
> Somehow I feel, that it runs not all too fast. I tried to use all the 
> possible speed-up options which I am aware of. I wonder if there are other 
> possibilities to increase the performance.
> For instance the monomer B calculation is exactly the same as the monomer A 
> one...
>
> I would be very grateful for any hints and suggestions (input is attached).
>
> Best regards
> 	R. Berger

Dr. Tatiana Korona http://tiger.chem.uw.edu.pl/staff/tania/index.html
Quantum Chemistry Laboratory
University of Warsaw
Pasteura 1, PL-02-093 Warsaw, POLAND


`The man who makes no mistakes does not usually make anything.'
                                        Edward John Phelps (1822-1900)