The theory of intermolecular force has advanced greatly in the last ten or fifteen years. The improved experimental and computational methods have made it possible to develop much more meticulous descriptions, and simple empirical models are no longer adequate to account for the detailed and accurate experimental measurements that are now available. Therefore a knowledge of advanced mathematical techniques is essential. The Theory of Intermolecular Forces is the first book to fully describe these techniques. Stone explains recent advances and sets out the mathematical techniques needed to handle the more elaborate models being used increasingly by both theoreticians and experimentalists in spectroscopy, molecular dynamics, and molecular modelling. Techniques described include the use of higher-rank multipole moments to describe electrostatic interactions, Cartesian and spherical tensor methods, and modern ab initio perturbation theories of intermolecular interactions