From owner-chemistry@ccl.net Mon Dec 23 15:29:00 2013 From: "Fedor Goumans goumans%scm.com" To: CCL Subject: CCL: Interpretation of TDDFT results Message-Id: <-49479-131223152425-26938-gckD6xZjvny/y/GQs9Dd1g ~ server.ccl.net> X-Original-From: Fedor Goumans Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Date: Mon, 23 Dec 2013 21:24:19 +0100 MIME-Version: 1.0 Sent to CCL by: Fedor Goumans [goumans,+,scm.com] Dear Radek, Perhaps the Annual Reviews paper by Casida and Huix-Rotllant is instructive. Paragraph 2.2 describes excitations in a two-electron two-orbital system. http://www.annualreviews.org/doi/abs/10.1146/annurev-physchem-032511-143803 Best wishes, Fedor On 12/23/2013 8:31 AM, Radoslaw Kaminski rkaminski.rk*|*gmail.com wrote: > Sent to CCL by: "Radoslaw Kaminski" [rkaminski.rk]*[gmail.com] > Dear All, > > I would like to ask a question regarding the practical interpretation of TDDFT results. When I do the TDDFT calculation I get a set of computed transitions, allowed and forbidden (e.g. S0 state -> T1 state). Later, in the output of various programs, there are shown as mixtures of some 'orbital transitions', with some coefficients. For example ADF prints out: > > 9: 405a -> 408a 0.9449 > 9: 406a -> 409a 0.0464 > 9: 400a -> 407a 0.0038 > 9: 401a -> 407a 0.0027 > 9: 405a -> 409a 0.0002 > > I was looking for a nice literature or tutorials how to practically interpret such results, unfortunately with no significant results. The thing I am a bit puzzled with is the relation of such 'mixed' transitions to the one-determinant approximation, which is used in the practical implementation of the DFT method. The S0 state has no unpaired electrons, T1 has two: one electron on former HOMO (now SOMO), and the other one on former LUMO (now other SOMO), and other excited configurations can be expressed in a similar way. Why then some of the computed transitions engage many orbitals with various contributions? What does it mean? Some nice tutorials or literature would be of a very much advantage for me. > > Thanks in advance. > > Best wishes, > > Radek> > -- Dr. T. P. M. (Fedor) Goumans Business Developer Scientific Computing & Modelling NV (SCM) Vrije Universiteit, FEW, Theoretical Chemistry De Boelelaan 1083 1081 HV Amsterdam, The Netherlands T +31 20 598 7625 F +31 20 598 7629 E-mail: goumans]*[scm.com http://www.scm.com