From chemistry-request@ccl.net Fri May 30 00:40:42 2003 Received: from smtp1.server.rpi.edu (smtp1.server.rpi.edu [128.113.2.1]) by server.ccl.net (8.12.8/8.12.8) with ESMTP id h4U4eggC028114 for ; Fri, 30 May 2003 00:40:42 -0400 Received: from webmail.rpi.edu (webmail.rpi.edu [128.113.26.21]) by smtp1.server.rpi.edu (8.12.9/8.12.9) with ESMTP id h4U4eeCR016134; Fri, 30 May 2003 00:40:40 -0400 Message-Id: <200305300440.h4U4eeCR016134-.at.-smtp1.server.rpi.edu> Content-Type: text/plain Content-Disposition: inline To: lou-.at.-scripps.edu From: "Dr. N. SUKUMAR" Organization: Rensselaer Polytechnic Institute Cc: chemistry-.at.-ccl.net, tlovell-.at.-scripps.edu, wengehan-.at.-scripps.edu, ithink-.at.-san.rr.com, sharples-.at.-scripps.edu, himo-.at.-TheoChem.kth.se X-Originating-Ip: 128.113.135.209 Mime-Version: 1.0 Reply-To: "Dr. N. SUKUMAR" Date: Fri, 30 May 2003 0:40:40 EDT X-Mailer: EMUmail 4.00 Subject: Re: CCL:Orbitals and Reality X-Scanned-By: MIMEDefang 2.28 Dr. Noodleman, I hate to quibble with what you've written, since you've expressed things so clearly, and I agree with most of what you say, but... > In general, I think of orbitals as somewhat real, less than electron > densities, or atoms, > but more than Lewis bond structures (at least, most of the time). I think of orbitals as somewhat LESS real than "Lewis bond structures" since in most cases the latter can be uniquely derived from topological analysis of the (real) electron-density, i.e. from the gradient paths and critical points thereof, whereas individual one-electron orbitals for many-electron systems, however useful they might be, are quite arbitrary; orbitals are solutions to a mathematical equation for a model system and will differ depending upon the model employed (Huckel, Hartree-Fock, Kohn-Sham, natural orbitals). With all due respect to the stalwarts of quantum mechanics, it makes little sense today to use terms like "physical reality" which cannot be defined with the degree of rigor we expect in science, without employing circular logic. And how to define "think" and "I" without invoking open systems and wavefunction collapse? Why, I'll be glad if we can all agree on the meaning of the word "is"! Dr. N. Sukumar http://www.drugmining.com/ Visiting Scientist Rensselaer Department of Chemistry and Wadsworth Center, New York State Dept.of Health