[molpro-user] DFT-SAPT and CCSD-SAPT for homodimers

[Tatiana Korona]

Dear Leonid,

In principle you are right about a waste of time by calculating monomer 
properties twice when monomers are identical, Note however that monomers are 
usually calculated in a dimer basis (or monomer-plus some functions on another 
monomer basis), and in general they are not identical for two reasons: 1) 
monomer positions wrt to each other are not equivalent (most cases if monomers 
are something more complicated than atoms), 2) even if they are equivalent, for 
degenerate MOs (say px and py pair) a transformation would be necessary in order 
to obtain properties of the second monomer in a common basis set, what is tricky 
in general. Therefore in all programs known to me identical monomers are 
calculated twice. It is simpler and safer.

Best wishes,

Tatiana

On Mon, 3 Oct 2016, Leonid Shirkov wrote:

> Dear Molpro Authors,
>
> as I understand,  there is no need to calculate the monomer properties
> twice for homodimers.
> Currently there is no way to treat homodimers as a special case, isn't it?
>
> Implementation of such option in Molpro could reduce the computational
> cost of SAPT for homodimers.
>
> Leonid
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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