Calculation of molecular polarizabilities using an anisotropic atom point dipole interaction model which includes the effect of electron repulsion

Abstract

The point dipole interaction model for molecular polarizability recently proposed by Applequist, Carl, and Fung is modified by replacing isotropic atomic point dipoles with anisotropic atomic point dipoles. The modified formalism, which is invariant to coordinate transformations, requires an additional empirical parameter for each atom type (ξA, the atomic anisotropy constant) and a single, global parameter applicable to all nonconjugated systems (κ, the repulsion exponent). The atomic polarizability tensor in the molecular environment is evaluated as a function of interatomic electron repulsion. This latter quantity is shown to be related to the degree to which bonding diminishes the polarizability of an atomic center in the direction (s) of the covalent bond (s). The anisotropic atom point dipole interaction model generates identical mean molecular polarizabilities as in the isotropic procedures of Applequist et al., while reducing the average error in the calculated molecular polarizability components to ∼7%. This error is comparable to experimental uncertainty.