Elsevier

Chemical Physics Letters

Volume 278, Issues 4–6, 31 October 1997, Pages 285-290
Chemical Physics Letters

Epstein-Nesbet second-order perturbation treatment of dynamical electron correlation and ground state potential energy curve of Cr2

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Abstract

The Cr2 potential energy curve is obtained by treating the dynamical correlation energy terms using a CI procedure based on determinants, equivalent to multi-reference second-order perturbation theory with the Epstein-Nesbet partition of the Hamiltonian. One of the advantages of this treatment is that the level shifts required for the equivalent Møller-Plesset type of treatment to eliminate intruder states and avoid divergences in the ground state second-order energy expression, are not required. Moreover, by truncating the reference space, the dynamical and the non-dynamical correlation energy is included also for the 3s, 3p electrons. The potentials are compared to experiment and to the most accurate theoretical potential curves in the literature.

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