Electron gas predictions of interatomic potentials tested by ab initio calculations

Abstract

The reliability of different variants of the electron gas density functional method for calculating the interaction energy of two closed-shell systems is examined. This is achieved by comparing the short range potentials predicted by electron gas theory with values which are exact within the assumption that the electron densities of the interacting atoms remain undistorted. It is concluded that, for systems which are adequately described by electron gas theory, the variant of Lloyd and Pugh [1] will be most reliable. It is shown that electron gas theory may fail for systems in which one or more of the occupied valence orbitals on one of the atoms has a symmetry with respect to the molecular environment which is different from that of any occupied valence orbital belonging to the other atom.