title: A cumulant functional for static and dynamic correlation.
abstract: A functional for the cumulant energy is introduced. The functional is composed of a pair-correction and static and dynamic correlation energy components. The pair-correction and static correlation energies are functionals of the natural orbitals and the occupancy transferred between near-degenerate orbital pairs, rather than the orbital occupancies themselves. The dynamic correlation energy is a functional of the statically correlated on-top two-electron density. The on-top density functional used in this study is the well-known Colle-Salvetti functional. Using the cc-pVTZ basis set, the functional effectively models the bond dissociation of H2, LiH, and N2 with equilibrium bond lengths and dissociation energies comparable to those provided by multireference second-order perturbation theory. The performance of the cumulant functional is less impressive for HF and F2, mainly due to an underestimation of the dynamic correlation energy by the Colle-Salvetti functional.
authors: Department of Chemistry, University of Winnipeg, Winnipeg, Manitoba R3B 2G3, Canada.
authors: Joshua W
authors: JW
authors: Hollett
authors: Department of Chemistry, University of Winnipeg, Winnipeg, Manitoba R3B 2G3, Canada.
authors: Hessam
authors: H
authors: Hosseini
authors: Department of Chemistry, University of Winnipeg, Winnipeg, Manitoba R3B 2G3, Canada.
authors: Cameron
authors: C
authors: Menzies