Analysis of the Contributions to the Kinetic and Potential Energies of an H Atom in the Presence of a Point Charge: The Molecular Virial Theorem Revisited.

The molecular virial theorem states that for a diatomic molecule or for an atom in the presence of a point charge, the changes in the average kinetic energy and average potential energy are equal to [Formula: see text] and [Formula: see text], respectively, where U is the interaction energy and R is the internuclear separation or the atom-point charge separation. In this paper we directly evaluate the ⟨T⟩ and ⟨V⟩ expectation values of an H atom in the presence of a distant point charge, obtaining exact analytical expressions by use of Dalgarno-Lewis perturbation theory.