Subject: Spin contamination

From: [email-masked]
Date: Fri, 15 Jan 1999 10:48:02 +0100 (NFT)

Dear CCL'ers

I am studying the OO bond cleavage in the secondary ozonide (in order to
form a biradical .OCH2OCH2O. ) at the MP2 and DFT level (singlet state).
The barrier heights computed with Gaussian94 are :

UMP2/6-31G** = 43.4 kcal/mol
Annihilation of the first spin contaminant:
S**2 before annihilation      .8871,   after      .0785

PMP2/6-31G** = 20.9 kcal/mol

UB3LYP/6-31G** = 20.8 kcal/mol
Annihilation of the first spin contaminant:
S**2 before annihilation      .7684,   after      .0234

I would know your opinion about the reliability of this PMP correction in
which the largest spin contaminant is annihilated. What about the spin
contamination in the UB3LYP method (PMP2 and UB3LYP are very close...) ?
References are welcome.

I will summarize.
Thanks a lot.

Phil

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APLINCOURT Philippe
Laboratoire de Chimie Theorique
UMR 7565 Structure et Reactivite des Systemes Moleculaires Complexes
Faculte des Sciences, Domaine Scientifique Victor Grignard B.P. 239
54506 VANDOEUVRE-LES-NANCY Cedex
Tel    : 03 83 91 20 00   Poste 35 52
Fax    : 03 83 91 25 30
E-mail : [email-masked]
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