Subject: electronic correlation

From: <[email-masked]>
Date: Fri, 4 Apr 1997 15:42:03 +0200 (MET DST)

Dear CCL,

My question is short: What's exactely the electronic correlation (dynamic and no dynamic correlation)?

	Many thanks for your help

				Sylvie Joanteguy

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From: "Dr. Heinz Schiffer" <[email-masked]>
Date: Fri, 04 Apr 1997 17:29:16 +0200

>         Many thanks for your help

Hi Sylvie,
the definition of the correlation energy is

	E_corr = E_exact - E_HF

E_exact is the exact nonrelativistic energy eigenvalue of the
electronic Schroedinger equation. E_HF is the corresponding 
Hartree-Fock energy (basis set limit !). That definition goes
back to Loewdin. Sinanoglu was the first who introduced the terms
'dynamic' and 'non-dynamic' correlation, the latter one arises
because of degeneracies or near-degeneracies of electronic systems.
A good and very recent discussion of this subject can be found in the
paper

Daniel K. W. Mok, Ralf Neumann, and Nicholaus C. Handy
J. Phys. Chem. 100 (1996) 6225-6230

Ciao,
Heinz 
-- 
Dr. Heinz Schiffer		Phone   ++49-69-305-2330
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