From chemistry-request*- at -*server.ccl.net Tue Jul 23 17:11:49 2002 Received: from deluge.cc.mcgill.ca ([132.206.27.50]) by server.ccl.net (8.11.6/8.11.0) with ESMTP id g6NLBnr00854 for ; Tue, 23 Jul 2002 17:11:49 -0400 Received: from dna.mcgill.ca (dna.McGill.CA [132.206.27.48]) by deluge.cc.mcgill.ca (8.12.3/8.11.0) with ESMTP id g6NLBir1004025 for ; Tue, 23 Jul 2002 17:11:48 -0400 (EDT) Received: from mcgill (ariya3.Chem.McGill.CA [132.206.175.121]) by dna.mcgill.ca (8.12.2/8.12.0) with ESMTP id g6NLBaoo012006 for ; Tue, 23 Jul 2002 17:11:44 -0400 (EDT) From: "Alexei Khalizov" To: chemistry ^at^ ccl.net Date: Tue, 23 Jul 2002 17:11:36 -0400 MIME-Version: 1.0 Subject: A problem with O(1D) Reply-to: alexei.khalizov&$at$&mcgill.ca Message-ID: <3D3D8E3C.28301.4E99E562&$at$&localhost> Priority: normal X-mailer: Pegasus Mail for Windows (v4.01) Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Content-description: Mail message body Dear CCLers, Does anyone know how to calculate correctly the energy of an oxygen atom in the singlet state O(1D)? I am having a problem of evaluating the singlet-triplet energy difference E(S-T) = E[O(1D)] - E[O(3P)] whose experimental value is 190 kJ/mol. Using DFT methods (B3LYP and PW91) with small basis sets (6-31G*) significantly overestimates this energy splitting, giving E(S-T) = 270-280 kJ/mol. Calculation at CCSD(T)/6-311+G(3df) level of theory leads to a better result, however, it is still far from being acceptable, E(S-T) = 214 kJ/mol. So far I have found that it is the energy of O(1D) that is incorrect while the energy of O(3P) is reproduced properly. What goes wrong? The wavefunction for O(1D) seems to be correct - population analysis shows that it is symmetrical (2Px alpha) (2Px beta) (2Py alpha) (2Py beta). Thank you in advance, Alexei ------------------------- Dr. Alexei Khalizov Department of Chemistry McGill University, 801 Sherbrooke St. W., Montreal, Quebec, CANADA, H3A 2K6 Phone: (514) 398-6920 Fax: (514) 398-2382