United Atom Treatment of the Behavior of Potential Energy Curves of Diatomic Molecules for Small <i>R</i>

Abstract

It is shown that the potential energy function V (R) of any state of a diatomic molecule can be expanded for small internuclear distances, in the from V(R)=[(ZaZb)/R]+Wu+E2·R2+E3·R3+···, where Wu is the energy of that state of the united atom to which the molecular state under consideration connects. Explicit expressions for the coefficients E2, E3 are given in terms of the electronic charge density of the united atom. Applications of the derived energy expansion are discussed.