Subject: Spin corrected single-determinant wave functions, energies and gradients

From: Nicolas Ferré <nicolas.ferre^at^up.univ-mrs.fr>
Date: Mon, 07 Jun 2004 15:14:49 +0200

Dear ccl,

I am looking for a program able to compute a reaction path, or at least 
geometry optimizations, using spin corrected single-determinant 
wavefunction (HF, MP, CC ...), energies and gradients when large spin 
contamination occurs. I am aware of the spin projection techniques, a 
priori or a posteriori, the later being implemented e.g. in gaussian but 
I don't believe gradients are coded in (I think a population analysis 
can be done using a spin projected wfn).
Because the systems I want to study are of medium size to large size, I 
cannot really consider multi-reference methods (unfortunately).
By the way, Chen and Schlegel published in 96 that projected dft is even 
worse than unrestricted dft. Is there any alternative technique for 
using dft when large spin contamination occurs (yes, even at the dft 
level) ? Or should I, in any case, use a non hybrid functional ?

Best regards,

-- 
  Dr. Nicolas Ferre'
  Laboratoire de Chimie Theorique et de Modelisation Moleculaire
  UMR 6517 - CNRS Universite' de Provence
  Case 521 - Faculte' de Saint-Jerome
  Av. Esc. Normandie Niemen
  13397 MARSEILLE Cedex 20 (FRANCE)
  Tel : (+33)4.91.28.27.33              Fax : (+33)4.91.28.87.58