Calculation of the Attractive He Pair Potential

Abstract

The symmetry-adapted pair-correlation energy of diatomic helium was evaluated for five internuclear separations near the potential minimum by means of localized orbitals obtained from transformation of a molecular Hartree-Fock wave function. An attractive potential depth of 12.0\ifmmode^\circ\else\textdegree\fi{}K at $R=2.96$ \AA{} was obtained in agreement with the best experimental estimates, leading to the conclusion that the omitted electron correlation within the helium atom does not affect the interatomic correlation energy by more than about 10%. This result is in essential agreement with that obtained independently by Bertoncini and Wahl. The electron correlation contribution is divided into $\ensuremath{\sigma}$, $\ensuremath{\pi}$, and $\ensuremath{\delta}$ parts as well as into its atomic symmetry so as to elucidate the magnitude of the various contributions.