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

✍ Scribed by Andrzej Leś; Ludwik Adamowicz

Publisher
Elsevier Science
Year
1991
Tongue
English
Weight
581 KB
Volume
183
Category
Article
ISSN
0009-2614

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✦ Synopsis

The originally proposed first-order correlation orbital method (L. Adamowicz and R.J. Bartlett, J. Chem. Phys. 86 ( 1987) 63 14) 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 et al. (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.

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