From chemistry-request*- at -*server.ccl.net Sun Jun 23 13:25:29 2002 Received: from sg7.chemie.uni-konstanz.de ([134.34.7.80]) by server.ccl.net (8.11.6/8.11.0) with ESMTP id g5NHPSQ30749 for ; Sun, 23 Jun 2002 13:25:28 -0400 Received: from sg8.chemie.uni-konstanz.de (sg8.chemie.uni-konstanz.de [134.34.7.81]) by sg7.chemie.uni-konstanz.de (8.9.3/8.9.3) with ESMTP id TAA1247669; Sun, 23 Jun 2002 19:21:47 +0200 (CEST) Received: from localhost (hein -A_T- localhost) by sg8.chemie.uni-konstanz.de (8.9.3/8.9.3) with ESMTP id TAA601570; Sun, 23 Jun 2002 19:21:46 +0200 (MDT) Date: Sun, 23 Jun 2002 19:21:45 +0200 From: Frank Schaper Reply-To: To: cc: "Deng, Jun" , "Peter W. Thulstrup" Subject: Summary: DFT on openshell-Systems Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Dear Netters, thanx for the fast response to: "Deng, Jun" , "Per-Ola Norrby" , Stefan Grimme , Tomasz Borowski , Sorana Ionescu , Antonia de Noronha and Frank Neese . Here is requested summary: - Is a strong dependence on the DFT-functional a "normal" behavior for open-shell systems? The answer was a general "yes" from all experts. Sometimes even orbital orders differ with the chosen functional. The local density approximation (VWN-functional) was regarded a bad choice anyway. In general, DFT seems to prefer lower spin states in contrast to HF-methods. - Is there any way to take a shortcut for geometry optimizations? E.g. calculating the geometry closed-shell and using single-point energies for different open-shell spin states. - Is a geometry optimization mandatory for every spin state (possible in my case S=1, 3 and 5) or are single-point calculations sufficient? I'm very much afraid they are not. Summarizing the answers to both questions, it seems to be necessary to optimize every geometry with the functional used for the energy calculations. Geometries should also be optimized for every spin state (that was a silly question in any case). - Can the calculated energies of the same complex with different spin states be compared directly or is the spin-pairing-energy missing to some extend? Here the opinions seem to differ a little bit. As far as I have understood, energies of different spin states can be compared, i.e. the spin pairing energy is included in the calculated energies. On the other hand, single-determinant DFT-methods seem to have problems describing lower spin states and the relative energies (though they can be compared in principle) are rather qualitative up to wrong. Multi-configuration methods were proposed to give better results. Thanks again for the responses. Hein -- Frank (Hein) Schaper - AG Brintzinger - Universitaet Konstanz email : Frank.Schaper |-at-| uni-konstanz.de - Frank |-at-| Schaper.com mail $#at#$ FrankSchaper.de web : www.FrankSchaper.de s-mail : Frank Schaper - AG Brintzinger - Universitaetsstr. 10 78434 Konstanz