From chemistry-request@server.ccl.net Tue Sep 12 23:17:00 2000 Received: from uvaix7e1.comp.UVic.CA (root@uvaix7e1.comp.UVic.CA [142.104.5.107]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id XAA11331 for ; Tue, 12 Sep 2000 23:16:59 -0400 Received: from p17-78.dialup.UVic.CA (p17-78.dialup.UVic.CA [142.104.17.78]) by uvaix7e1.comp.UVic.CA (8.9.3/8.9.3) with SMTP id UAA83136 for ; Tue, 12 Sep 2000 20:16:52 -0700 From: Roy Jensen To: CHEMISTRY@ccl.net Subject: Deduction of electronic properties from Gaussian output. Date: Tue, 12 Sep 2000 20:18:06 -0700 Message-ID: X-Mailer: Forte Agent 1.8/32.548 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by server.ccl.net id XAA11332 Thanks to those of you who have aided in my use of ab initio calculations thus far. With your help, I was able to get several transition metal cluster calculations running. Our lab uses mass spectrometry and spectroscopy to detect and characterize species. I was asked a question I cannot answer. That, of course led to more questions... 0. Many texts and manuals explain how to do quantum chemistry or use ab initio packages. Is there an introductory reference that explains how to extract information from the output, Gaussian in this case? 1. How can I tell if I need to use guess=alter? 2. Is it reasonable to run the same complex as a singlet, triplet, quintet, and septet and determine the ground state multiplicity as the job that has the lowest energy? 3. I generally run NBO analysis on these complexes. How do I determine the electronic angular momentum? 4. Is it reasonable to _estimate_ allowed and forbidden electronic transitions by using the orbital energy levels provided from the optimized geometries? I understand that CIS and CASSCF calculations would provide better results. I have been using the UB3LYP/LANL2DZ basis set for the calculations; MP2/anything takes too long to converge. Roy Jensen