The theory of nonlinear dielectrics. Polar, polarizable molecules

Abstract

Some aspects of the nonlinear dielectric behavior of a simple fluid composed of polar, polarizable particles having spherical hard cores are discussed. In particular, the connection between the lowest order nonvanishing nonlinear dielectric constant and fluctuations in the polarization and dipole densities is found. By ignoring certain high order fluctuations, the nonlinear dielectric constant is related to two, three, and four body correlation functions. A further approximation involving the neglect of short range angular correlations produces the analog of the Onsager connection for the linear dielectric constant. The connections given here differ from all previous proposals. Some examples are given to illustrate the relative importance of electrostriction, anisotropic polarizabilities, and permanent dipole moments and the difference with previous proposals.