Alignment of polarizable dipoles on a lattice

The alignment average of polar molecules may be derived from their NMR spectrum, when a strong electric field is applied to the liquid. The Kerr effect can likewise be related to the alignment.In this paper the alignment has been calculated for a rigid-lattice model, previously developed by Van Vleck in the theory of dielectric polarization and extended by others. A series expansion of the alignment for a system of isotropically polarizable dipoles is presented up to second-order terms in the dipolar interaction. The result for a continuum has been compared with those calculated on the basis of the Lorentz and Onsager model of the liquid.An explicit expression for the total electrostatic energy of a binary mixture of polar and non- polar molecules with a symmetric polarizability tensor has also been calculated; it has been obtained from a generalization of a formalism, developed by Mandel and Mazur for the pure polar liquid.