From owner-chemistry@ccl.net Wed Nov 9 11:04:01 2005 From: "errol lewars elewars-x-trentu.ca" To: CCL Subject: CCL:G: transition state searches with CASSCF ??? Message-Id: <-29910-051109102832-10194-Wk+b5qgVNseNQqT8BPfVZQ{}server.ccl.net> X-Original-From: errol lewars Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii; format=flowed Date: Wed, 09 Nov 2005 10:26:17 -0500 MIME-Version: 1.0 Sent to CCL by: errol lewars [elewars-,-trentu.ca] 2005 Nov 9 Hello, Yes, it is possible to find a TS at the CASSCF level with G03 (I used revision B.05); see J Phys Chem 2005, 109(43), 9827-9830. Start with a HF or MP2 structure, say, for the input geometry. Use corresponding MOs for the active space in comparing reactant, TS, and product. However your reaction, in which closed-shell molecules are transformed into radicals may give special problems in calculating the activation energy. EL ==== Theo de Bruin theodorus.de-bruin!^!ifp.fr wrote: >Sent to CCL by: "Theo de Bruin" [theodorus.de-bruin%a%ifp.fr] >Hello > >I wish to know whether it is possible to perform transition state searches at the CASSCF level of theory using Gaussian 03 rev C02. I asked the same question to the helpdesk of Gaussian but I gave up, after waiting more than 5 weeks. >I would like to study a bi-molecular reaction in which two (neutral) molecules are transformed into two radicals (reversed dismutation reaction). >Neither B3LYP nor X3LYP are capable to locate the TS, while unrestricted MP2 gives the correct TS but unusual high barrier (delta H activation) and delta H are obtained. > >Thanks for sharing your thoughts how to handle this problem. > >Kind regards, > >Theo de Bruin >theodorus.de-bruin . ifp.fr> > > > >