CCL: spin contamination and S**2



 Sent to CCL by: "Xavier ASSFELD" [Xavier.Assfeld()cbt.uhp-nancy.fr]
 --Replace strange characters with the "at" sign to recover email
 address--.
 Hi,
 for S**2 pronounce "S squared" (S multiplied by S). It is the
 expectation
 value of the total spin operator.
 If for a wavefunction of a singlet you get a S**2 value greater than 0 then
 it is spin contaminated. Spin contamination can only arises with states of
 higher multiplicity and of the same parity (odd or even) than the desired
 state.
 Hope this helps.
 			       ...Xav
 Pr. Xavier Assfeld             Xavier.Assfeld()cbt.uhp-nancy.fr
 Chimie et Biochimie theoriques T: (33) 3 83 68 43 82
 Faculte des Sciences           F: (33) 3 83 68 43 71
 54506 Vandoeuvre, France       http://www.cbt.uhp-nancy.fr
 X> -----Message d'origine-----
 X> De?: owner-chemistry()ccl.net [mailto:owner-chemistry()ccl.net]
 X> Envoye?: dimanche 18 septembre 2005 22:29
 X> A?: Assfeld, Xavier
 X> Objet?: CCL: spin contamination and S**2
 X>
 X>
 X>
 X> Sent to CCL by: "Telkuni Tsuru" [telkuni^^venus.dti.ne.jp]
 X>
 X> --Replace strange characters with the "at" sign to recover email
 X> address--.
 X>
 X> Hello, Callers.
 X>
 X> I like to ask the relationship between the spin contamination and
 X> S**2 value.
 X>
 X> As mentioned before, S**2 shows the spin state, singlet(=0 [+/- 10%]),
 X> doublet (=0.75 [+/- 10%]), triplet (=2.0 [+/- 10%]), etc. When one
 X> molecule's multiplicity is singlet and its S**2 is 0.5, can I say that
 X> the molecule has spin contamination ?
 X> And the same manner, the multiplicity is doublet and its S**2 is 1.2,
 X> can I say that the molecule has spin contamination too ?
 X>
 X> (What should I call "S**2"?  Is it "S star 2"?)
 X>
 X>   All responses, I will appreciate.
 X>   I will summarize them and send to CCL.
 X>
 X>
 X>   Thanks in advance
 X> ---------------------------------------------------
 X>        Telkuni Tsuru     telkuni()venus.dti.ne.jp
 X>
 X>
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