From owner-chemistry@ccl.net Mon May 6 07:51:14 1996 Received: from bedrock.ccl.net for owner-chemistry@ccl.net by www.ccl.net (8.7.1/950822.1) id HAA15260; Mon, 6 May 1996 07:42:34 -0400 (EDT) Received: from hp.rz.uni-potsdam.de for kallies@serv.chem.uni-potsdam.de by bedrock.ccl.net (8.7.1/950822.1) id HAA17619; Mon, 6 May 1996 07:42:23 -0400 (EDT) Received: from serv.chem.uni-potsdam.de by hp.rz.uni-potsdam.de with SMTP (1.37.109.10G/16.2) id AA132892632; Mon, 6 May 1996 13:37:12 +0200 Received: from pch10.chem.uni-potsdam.de by serv.chem.uni-potsdam.de (AIX 3.2/UCB 5.64/4.03) id AA24273; Mon, 6 May 1996 13:37:56 +0100 Date: Mon, 6 May 1996 13:37:56 +0100 Message-Id: <9605061237.AA24273@serv.chem.uni-potsdam.de> X-Sender: kallies@serv.chem.uni-potsdam.de X-Mailer: Windows Eudora Light Version 1.5.2 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" To: gadre@cdac.ernet.in From: "B. Kallies" Subject: Re: CP correction to BSSE Cc: chemistry@ccl.net 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: kallies@serv.chem.uni-potsdam.de Fax: ++49 / 0331 977 1315 ---------------------------------------------------