Dear Vega > Do the both calculation output the singlet state energy?
They are two different states: 'spin=2, multiplicity=1' --> Here you can deal with a system with two, spatially different, single-electron KS wavefunctions, occupied by one 'up' electron and one 'down' electron. This can be called an "open shell singlet" You could find that: a) your total magnetization is 0.00 mB, because this is forced by the 'multiplicity=1' keyword, but your absolute magnetization could be, say, 2.00 mB, a sort of antiferromagnetic system; b) the energy difference with a real triplet, in this case, could be almost negligible, so that the system could be considered a triplet forced in this state due to the 'multiplicity=1' constraint 'spin=1' --> Here you are forcing a restricted representation of your system, that is, you have KS wavefunctions that can be occupied by a couple of paired electrons. Which is the 'best' singlet? You should know, depending upon the properties of your system. Hope this help Giuseppe On Wednesday 13 January 2010 11:11:14 vega lew wrote: > Dear sir, > > Do the both calculation output the singlet state energy? > If I want to compare the energy difference of singlet and triplet, which > calculated singlet state energy should be used? > > thank you for your help. > > best wishes, > > vega > > On 1/13/2010 14:43, Paolo Giannozzi wrote: > > On Jan 13, 2010, at 6:41 , vega lew wrote: > >> I have compare the results of two calculation for singlet state > >> with or without the option 'spin=2, multiplicity=1'. > > > > they aren't the same. A non-polarized calculation will yield S^2=0, > > Sz=0. > > A spin-polarized calculation with "multiplicity=1" will yield Sz=0 > > but not > > necessarily S^2=0. See for instance J. Phys. Chem. B 105, 11227 > > (2001) for a nice description of how neglecting to appreciate such > > difference may lead to unphysical results. > > > > P. > > --- > > Paolo Giannozzi, Dept of Physics, University of Udine > > via delle Scienze 208, 33100 Udine, Italy > > Phone +39-0432-558216, fax +39-0432-558222 > > > > > > > > _______________________________________________ > > Pw_forum mailing list > > Pw_forum at pwscf.org > > http://www.democritos.it/mailman/listinfo/pw_forum -- ******************************************************** - Article premier - Les hommes naissent et demeurent libres et ?gaux en droits. Les distinctions sociales ne peuvent ?tre fond?es que sur l'utilit? commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la libert?, la propri?t?, la s?ret? et la r?sistance ? l'oppression. ******************************************************** Giuseppe Mattioli CNR - ISTITUTO DI STRUTTURA DELLA MATERIA v. Salaria Km 29,300 - C.P. 10 I 00016 - Monterotondo Stazione (RM) Tel + 39 06 90672836 - Fax +39 06 90672316 E-mail: <giuseppe.mattioli at ism.cnr.it> -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20100114/d18844c9/attachment.htm
