Gaussian03: MP2 before CI or CC
- From: Nicolas Ferré
- Organization: LCTMM
- Subject: Gaussian03: MP2 before CI or CC
- Date: Tue, 14 Dec 2004 16:14:47 +0100
When you run a CI or CC job with g03, it starts by resolving the HF
equations. In the next step, the integrals are expressed over MOs and
then the first-order MP wavefunction (and the second-order MP energy)
are computed, all of this done in the link 804. Finally, g03 uses these
informations for the CI or CC job in the link 913.
I would like to find references about this procedure. I guess it is
related to the Davidson scheme for diagonalizing the CI matrix. But why
always using the MP wavefunction instead of the HF one ? Is there an
option in g03 for using the HF wavefunction ?
What is more surprising is that the CI or CC energy depends on the MO
eigenvalues ! I just slightly modified the code in link 801 for
one eigenvalue (rwf 547) and the final CI or CC energy varies with this
eigenvalue ! I checked the same behavior on different machines. Can
someone explain what is happening ? I guess I am missing something but
cannot find what.
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)188.8.131.52.33 Fax : (+33)184.108.40.206.58
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