Van der Waals induced dipoles

Abstract

Expressions are derived for calculating the induced dipole moment of an arbitrary molecule A interacting with an arbitrary system B through first- and second-order Coulomb interaction. The theory is formulated in terms of linear and quadratic charge-density susceptibilities and takes account of charge penetration but not exchange between the systems. The theory is specialized to the interaction of two nonoverlapping molecules and to a molecule interacting with a nonferroelectric solid, metallic, or crystalline. In the case of two interacting molecules, the induced moment is developed in inverse powers of R, the distance between the centers of the molecules, up to and including R−7; the coefficients of the series are given in terms of the total charges, permanent moments, polarizabilities, and hyperpolarizabilities. In the case of the solid, the results are given in terms of the molecule–solid distance z0, the dielectric function of the solid, and the permanent moments, polarizabilities, and hyperpolarizabilities of the molecule. The expressions for the dispersion and induction dipoles derived here in terms of the charge-density (hyper) susceptibilities are the most general to date in that ionic contributions are included, and the expansion in terms of the (hyper)polarizabilities is the most explicit for nonoverlapping systems. Our results are compared with the work in the literature.