Subject: Re: CP correction to BSSE

From: "B. Kallies" <[email-masked]>
Date: Mon, 6 May 1996 13:37:56 +0100

Dear Mr. Gadre,

the basis for understanding the counterpoise procedure by applying it
on dimers of polyatomic monomers is the idea that the process of complex
formation from infinitely separated molecules can be divided into two
processes, which form a thermodynamic cycle:
1) Deformation of the monomers when they approach each other.
2) Complex formation from the distorted monomers.
The first process needs "deformation energy", the second yields
"interaction energy". The sum of the two terms is called "association
energy" and equals to the reaction energy we normally write down and which
we want to correct in final. But only the interaction energy has to be corrected
for BSSE. The deformation energy is error free.
So, for estimating the BSSE of the interaction energy (which is also the
BSSE of the association energy) by the counterpoise procedure, use the
monomers in their geometry in the complex. For a more detailed description
including thermal corrections for BSSE-corrected association enthalpies see

B. Kallies and R. Mitzner, J. Mol. Model. 1995, 1, 68-78 (accessible through
WWW:

http://derioc1.organik.uni-erlangen.de/info/JMOLMOD/papers/papers.html)

Best regards
Kallies

---------------------------------------------------
DC Bernd Kallies
Institut fuer Physikalische und Theoretische Chemie
Universitaet Potsdam
Am Neuen Palais 10
14469 Potsdam
GERMANY
e-mail: [email-masked]
Fax: ++49 / 0331 977 1315
---------------------------------------------------