From chemistry-request \\at// server.ccl.net Fri Jul 28 03:45:23 2000 Received: from compchem.dfh.dk (compchem.dfh.dk [130.225.225.51]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id DAA27693 for ; Fri, 28 Jul 2000 03:45:22 -0400 Received: from [130.225.225.151] (dhcp225-151.dfh.dk [130.225.225.151]) by compchem.dfh.dk (SGI-8.9.3/8.9.3) with ESMTP id JAA13159 for ; Fri, 28 Jul 2000 09:44:45 +0200 (MEST) Mime-Version: 1.0 Message-Id: In-Reply-To: <397C5C3F.28DEEEDA $#at#$ eeyore.cm.utexas.edu> References: <397C5C3F.28DEEEDA- at -eeyore.cm.utexas.edu> Date: Fri, 28 Jul 2000 09:44:06 +0200 To: chemistry- at -ccl.net From: Per-Ola Norrby Subject: TM force fields Content-Type: text/plain; charset="us-ascii" ; format="flowed" Isaac B. Bersuker wrote: >I repeat my firm conviction that, in general, there are >no force fields for transitiom metal systems (see my latest book ... (The rest of the message deleted). I've seen this comment a couple of times now, and I'm getting irritated. This is a very sweeping statement, and insulting to those who have produced good work in this area. It is only true if you interprete it like "it is not possible to achieve infinite accuracy for all possible TM complexes", but stated like that it would be equally true of any method. For specific classes of complexes, it is possible to get high accuracy with force field methods. It's just a question of having a flexible enough force field and doing a careful parameterization. Check out the book by Comba and Hambley, "Molecular Modeling of Inorganic Compounds", a new edition is comming out soon. We also have a review in press in Coord.Chem.Rev. on how to do this parameterization (don't know when it's going to appear). For some classical reviews, see: C.R. Landis, D.M. Root, T. Cleveland, in: K.B. Lipkowitz and D.B. Boyd (Eds.), Reviews in Computational Chemistry, Vol. 6, VCH Publishers, Inc., New York, 1995, p. 73-148. M. Zimmer, Chem. Rev. 95 (1995) 2629. P. Comba, Comments Inorg. Chem. 16 (1994) 133. B.P. Hay, Coordination Chemistry Reviews 126 (1993) 177. (Yes, I know, I left several out, this is just a selection based on personal preference). The general force fields are also advancing. You can still get whooping errors, and should validate carefully, but I've actually been surprised several times by the results you can get without specific parameterization. I'd like to point to UFF (not all implementations though :-), VALBOND (not a complete force field, but a very interesting addition to UFF), and the force fields in PCModel and Spartan. There are others, but I don't have personal experience with them. Per-Ola -- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ * Per-Ola Norrby, Associate Professor * The Royal Danish School of Pharmacy, Dept. of Med. Chem. * Universitetsparken 2, DK 2100 Copenhagen, Denmark * Tel. +45-35306506, fax +45-35306040 * Email: peo \\at// dfh.dk (preferred), peo \\at// compchem.dfh.dk * WWW: http://compchem.dfh.dk/PeO/