Interactions between Oppositely Charged Nonspherical Ions. I. Potential Energy Function

Abstract

In this paper we apply the theory of Steele to the problem of determining the pairwise interactions between oppositely charged nonspherical ions imbedded in a vacuum. The diatomic model of Sweet and Steele was extended by superimposing at either end of each linear, symmetric rod a Coulombic center characterized by a r−1 distance dependence. With respect to the consequent charge—charge interactions, a value of the Onsager coupling parameter was chosen which allowed a more detailed study of the relative importance of Lennard-Jones versus Coulombic forces; in effect, the ions were assumed to be only partially charged. Coefficients in the expansion of the potential energy function were calculated numerically, and changes in the profiles of the resulting curves [Ul,l′,m(r) as a function of interionic distance] were noted for different values of R/σ (where R is the length of the rod and σ is the usual Lennard-Jones range parameter). The trends observed were compared with those found by Sweet and Steele in their study of the diatomic model.