From chemistry-request%!at!%www.ccl.net Mon Mar 15 08:56:01 1999 Received: from mail-b.bcc.ac.uk (mail-b.bcc.ac.uk [144.82.100.22]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with ESMTP id IAA09629 Mon, 15 Mar 1999 08:54:29 -0500 (EST) Received: from socrates-a.ucl.ac.uk by mail-b.bcc.ac.uk with SMTP (XT-PP); Mon, 15 Mar 1999 13:37:27 +0000 From: uccatvm Message-Id: <26272.199903151337(+ at +)socrates-a.ucl.ac.uk> Subject: Summary: polarizability and vdW radius for B To: chemistry \\at// www.ccl.net (CCL) Date: Mon, 15 Mar 1999 13:37:26 +0000 (GMT) X-Mailer: ELM [version 2.4 PL25] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Dear CCLers, A few weeks ago, I asked for a value for the polarizability and the van der Waals radius for B in a covalently bonded state. I would like to thank Wayne Steinmetz, Ajit J. Thakkar, and Robert J. Doerksen for their helpful replies. Wayne Steinmetz pointed me to the Allinger force field, which uses a van der Waals radius of 2.150 for covalently bonded B in the MM3 force field. The epsilon value is 0.014 kcal/mole. Ajit Thakker suggested the following papers: Das and Thakkar, J. Physics B, 31 (1998) 2215, for the polarizability of a free boron atom, while the polarizability of a boron atom in a heteroatomic molecule can be found from the parameters for model 5 in the 1998 JPCA paper by RJ Doerksen and AJ Thakkar (see below). Robert Doercksen pointed me to work from his Ph.D. thesis: "Azaborinines: Structures, vibrational frequencies, and polarizabilities," J. Phys. Chem. A 102, 4679-4686 (1998), RJ Doerksen and AJ Thakkar. In further work coming out in JPCA in 1999, their additive atom model of polarizability for 104 planar heteroaromatic molecules containing 5 or 6 of B, C, N, and O -- fitted to ab initio MP2 polarizabilities with an optimized basis set -- suggests that the polarizability of Boron in a planar heteroaromatic ring is about 15 a.u. Best regards, Tanja -- ==================================================================== Tanja van Mourik phone University College London work: +44 (0)171-504-4665 Christopher Ingold Laboratories home: +44 (0)1895-259-312 20 Gordon Street e-mail London WC1H 0AJ work: T.vanMourik ^%at%^ ucl.ac.uk United Kingdom home: tanja /at\netcomuk.co.uk ====================================================================