First-order correlation orbitals for the MCSCF zeroth-order wave function

Andrzej Leś, Ludwik Adamowicz

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


The originally proposed first-order correlation orbital method (L. Adamowicz and R.J. Bartlett, J. Chem. Phys. 86 (1987) 6314) has been extended in order to include the MCSCF zeroth-order wave function. The present method is based on the perturbation theory with the zeroth-order Hamiltonian suggested by Andersson (J. Phys. Chem. 94 (1990) 5483). In the present work we restrict our consideration to the simplest case, i.e. the two-electron/two-orbital MCSCF reference wave function. The procedure is tested on the model system - lithium dimer - at a variety of interatomic distances. The results show that the calculated second-order correlation energy as well as the value of the second-order Hylleraas functional in the reduced space of the first-order correlation orbitals behave correctly upon dissociation of the system.

Original languageEnglish (US)
Pages (from-to)483-490
Number of pages8
JournalChemical Physics Letters
Issue number6
StatePublished - Sep 13 1991

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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