Subject: Annihilation

From: "hu eric" <[email-masked]>
Date: Mon, 29 Jan 2001 10:47:24 -0800

Hi,

In DFT singlet or triplet diradical g98 output, there's a S**2 after 
annihilation. What is annihilation for? Does that mean I should use the new 
S**2 value as the reference? Thanks!

Eric
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From: Serguei Patchkovskii <[email-masked]>
Date: Mon, 29 Jan 2001 16:13:20 -0700 (MST)

> S**2 value as the reference? Thanks!

You should keep in mind that the "<S2>" expectation value, printed by 
Gaussian at the end of DFT calculations is not particularly meaningful 
in any case. This value is computed for the non-interacting Kohn-Sham 
reference wavefunction, and has no relation to the <S2> of the real, 
interacting system. The Gaussians' "<S2>" may be useful as a qualitative
indication of the degree of spin-contamination, but that's about it.

/Serge.P

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