From chemistry-request*- at -*server.ccl.net Sun Jul 9 12:23:55 2000 Received: from sunu450.rz.ruhr-uni-bochum.de (sunu450.rz.ruhr-uni-bochum.de [134.147.64.5]) by server.ccl.net (8.8.7/8.8.7) with SMTP id MAA27508 for ; Sun, 9 Jul 2000 12:23:54 -0400 From: Christoph.van.Wuellen: at :ruhr-uni-bochum.de Received: (qmail 11105 invoked from network); 9 Jul 2000 16:23:24 -0000 Received: from sgi249.rz.ruhr-uni-bochum.de (134.147.64.2) by mailhost.rz.ruhr-uni-bochum.de with SMTP; 9 Jul 2000 16:23:24 -0000 Received: (qmail 20826 invoked by uid 10283); 9 Jul 2000 16:23:10 -0000 Message-ID: <20000709162310.20825.qmail "-at-" sgi249.rz.ruhr-uni-bochum.de> Subject: Re: CCL:Are atoms spherical? To: amasunov ":at:" shiva.hunter.cuny.edu (AM) Date: Sun, 9 Jul 100 18:23:09 +0200 (MSZ) Cc: chemistry -A_T- ccl.net In-Reply-To: from "AM" at Jul 7, 0 04:03:16 pm X-Mailer: ELM [version 2.4 PL24] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Are atoms spherical? For an isolated atom, since the external potential is spherical, the "density" has to be spherical as well. For degenerate states, the "density" thus is the ensemble density. For an atom in an environment, there is no such argument. E.g. the density of a hydrogen atom will be deformed by the nearby presence of another hydrogen atom -- they form a bond. So, if atoms in VanDerWaals situations are nonspherical, this does not mean the "atom itself" is non-spherical. Nonspherical atoms as the result of a quantum-chemical calculations are a different topic, they mostly aris through symmetry breaking, that mostly is a defect of the chosen method. If, e.g. a fluorine atom is treated at the single-configuration level and if pz is chosen to be singly occupied, then the radial wave function of pz will be different from px and py --- no spherical density can be obtained even for an ensemble. This will change if one goes to a state-averaged calculation. Christoph van Wuellen