From chemistry-request@server.ccl.net Thu Feb 28 03:18:26 2002 Received: from smtp2.ruc.dk ([130.225.220.70]) by server.ccl.net (8.11.6/8.11.0) with ESMTP id g1S8IP525641 for ; Thu, 28 Feb 2002 03:18:25 -0500 Received: by smtp2.ruc.dk (Postfix, from userid 504) id D05681942CD; Thu, 28 Feb 2002 09:17:56 +0100 (CET) Received: from smtprelay.ruc.dk (smtprelay.ruc.dk [130.225.220.22]) by smtp2.ruc.dk (Postfix) with ESMTP id A78CE1942CA; Thu, 28 Feb 2002 09:17:55 +0100 (CET) Received: from virgil.ruc.dk (virgil.ruc.dk [130.225.220.110]) by smtprelay.ruc.dk (8.9.3+Sun/8.9.3) with ESMTP id IAA12652; Thu, 28 Feb 2002 08:48:28 +0100 (MET) Received: from VIRGIL/SpoolDir by virgil.ruc.dk (Mercury 1.47); 28 Feb 02 09:17:54 +0100 Received: from SpoolDir by VIRGIL (Mercury 1.47); 28 Feb 02 09:17:51 +0100 From: "Jens Spanget-Larsen" Organization: Roskilde Universitetscenter To: "Students of Dr. S. R. Gadre" Date: Thu, 28 Feb 2002 09:17:35 +0100 Subject: CCL: Correlation effect on .... Reply-To: spanget@ruc.dk Cc: chemistry@ccl.net Priority: normal X-mailer: Pegasus Mail for Windows (v2.23) Message-ID: <717C4917DCD@virgil.ruc.dk> "Students of Dr. S. R. Gadre": > CCLer's... > Could somebody give me a concrete example of weakly interacting > geometrical conformers where the energy trends reverse in correlated > methods.( One of the weakly interacting geometrical conformers which > was a lower energy minimum at Hartree Fock level should not be a > lower energy minimum in a correlated method like MP2 ...a conformer > which was not a lower energy minimum in Hartree Fock becoming a > lower energy minimum with a correlated method is the kind of > situation that i am looking for...the structures should be > stationary points on the PES) Dear Bala, the example of 1,6,6a-trithiapentalene may be of interest to you. Ab initio Hartree-Fock theory predicts an equilibrium geometry of Cs molecular symmetry, corresponding to a situation with two equivalent Cs symmetrical valence tautomers separated by a barrier of about 10 kcal/mol. Introduction of electron correlation effects (MP2, DFT) leads to the prediction of a single C2v symmetrical equilibrium geometry, consistent with the experimental evidence: K. B. Andersen, J. Abildgaard, J. G. Radziszewski, J. Spanget-Larsen, J. Phys. Chem. A 101, 4475 (1997) J. Spanget-Larsen, K. B. Andersen, Phys. Chem. Chem. Phys. 3, 908 (2001) Yours, Jens >--< NB! Please note new mail address: =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= JENS SPANGET-LARSEN Office: +45 4674 2710 Department of Chemistry Fax: +45 4674 3011 Roskilde University (RUC) Mobile: +45 2320 6246 P.O.Box 260 E-Mail: spanget@ruc.dk DK-4000 Roskilde, Denmark http://virgil.ruc.dk/~spanget =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=