A numerical test on the size consistency of some multireference configuration interaction approaches

The size consistency of selected multireference CI approaches is tested on two model problems, namely seven non-interacting H 2 molecules at their equilibrium bond length r e or at 2 r e and seven non-interacting Ne atoms. I n all cases the results obtained from the two-class CIPSI method (which is...

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Bibliographic Details
Published inChemical physics letters Vol. 200; no. 6; pp. 559 - 566
Main Authors Rubio, J., Povill, A., Illas, F., Malrieu, J.P.
Format Journal Article
LanguageEnglish
Published Amsterdam Elsevier B.V 25.12.1992
Elsevier Science
Subjects
Atomic and molecular physics
Electron correlation calculations for atoms and molecules
Electronic structure of atoms, molecules and their ions: theory
Exact sciences and technology
Physics
Total energy
Correlation energy
Hydrogen Molecules
Theoretical study
MR CI method
Numerical method
Electron correlation
Dissociation energy
Diatomic molecule
Neon Molecules
Models
Multiple excitation
Comparative study
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Summary:The size consistency of selected multireference CI approaches is tested on two model problems, namely seven non-interacting H 2 molecules at their equilibrium bond length r e or at 2 r e and seven non-interacting Ne atoms. I n all cases the results obtained from the two-class CIPSI method (which is an multireference MP2 procedure) are suprisingly good. The three-class CIPSI algorithm (which is an approximation of MR-SDCI) is much superior to SDCI, especially when the selection introduces the largest quadruply excited components. The implication of size-consistency error on dissociation energies is discussed.
ISSN:0009-2614
1873-4448
DOI:10.1016/0009-2614(92)80091-O