From owner-chemistry-: at :-ccl.net Fri Aug 13 09:56:01 2010 From: "Marcel Swart marcel.swart[A]icrea.es" To: CCL Subject: CCL: What is the meaning of minus value of Mulliken atomic spin densities? Message-Id: <-42523-100813095426-31225-vT9UqPQ0dFwthJqJeFZvaw . server.ccl.net> X-Original-From: Marcel Swart Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=iso-8859-1 Date: Fri, 13 Aug 2010 15:54:15 +0200 Mime-Version: 1.0 (Apple Message framework v1081) Sent to CCL by: Marcel Swart [marcel.swart]=[icrea.es] First, much depends on the spin polarization that you have given, i.e. in case of a doublet, if this doublet spin density should be in the alpha spins, or in the beta spins. (10 alpha 9 beta, vs. 9 alpha 10 beta) In principle, the sign of the spin densities should depend on this choice. Second, it depends if the program takes into account the electric charge for an electron or not. I.e. again looking at the 10alpha-9beta system, the total number of spin-polarized alpha-beta electrons is +1, with a corresponding total charge of -1. I'm almost certain that most programs report the -1 (charge) and not the number (+1), but I'm not sure. Third, Mulliken charges are known to be very basis set sensitive. Anyone of these factors influences your system, and even more so when you have a (transition) metal present. Marcel On Aug 13, 2010, at 1:48 PM, wangzc^iccas.ac.cn wrote: > Dear all, > > Recently I calculated a structure with MINUS value of Mulliken atomic spin densities,anyone can tell me how to understand that minus value? > > Thanks very much! =================================== dr. Marcel Swart ICREA Research Professor at Institut de Química Computacional Universitat de Girona Parc Científic i Tecnològic Edifici Jaume Casademont (despatx A-27) Pic de Peguera 15 17003 Girona Catalunya (Spain) tel +34-972-183240 fax +34-972-183241 e-mail marcel.swart!^!icrea.es marcel.swart!^!udg.edu web http://www.marcelswart.eu ===================================