On a mixed Moller-Plesset Epstein-Nesbet partition of the Hamiltonian to be used in multireference perturbation configuration interaction

Citation
C. Angeli et al., On a mixed Moller-Plesset Epstein-Nesbet partition of the Hamiltonian to be used in multireference perturbation configuration interaction, CHEM P LETT, 317(3-5), 2000, pp. 472-480
Citations number
25
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
CHEMICAL PHYSICS LETTERS
ISSN journal
00092614 → ACNP
Volume
317
Issue
3-5
Year of publication
2000
Pages
472 - 480
Database
ISI
SICI code
0009-2614(20000204)317:3-5<472:OAMMEP>2.0.ZU;2-X
Abstract
Within the frame of second-order multi-reference perturbation theory (MR-PT ), drawing on previous work of Dyall, a new partition of the Hamiltonian, w hich can loosely be considered as intermediate between Moller-Plesset (MP) and Epstein-Nesbet (EN), is presented. The method, which is well suited for CAS-SCF zero-order wavefunctions, is expected to correct partially the def ects of MP and EN while retaining their good properties. The new approach h as been successfully applied to some test cases involving the homonuclear d iatomics F-2, Cl-2 and N-2 where the faults of the EN treatment appear to b e in large measure eliminated. Application to the Cr, diatomic shows that t he dramatic intruder state problem suffered by the MP treatment is complete ly solved, affording a qualitatively good description of the potential ener gy curve for the ground state. (C) 2000 Elsevier Science B.V. All rights re served.