The field of Physical Chemistry has developed through the application of theories and concepts developed by physicists to properties or processes of interest to chemists. Physicists, being principally concerned with the basic ideas, have generally restricted their attention to the simplest systems to which the concepts applied, and the task of applying the techniques and theories to the myriad substances and processes that comprise chemistry has been that of the physical chemists. The field of Solid State Chemistry has developed with a major impetus from the synthetic chemists who prepared unusual, novel materials with the principal guid­ ing ideas growing out of an understanding of crystal structure and crystal structure relationships. The novel materials that pour forth from this chemical cornucopia cry out for further characterization and interpretation. The major techniques for the characterization and interpretation of crystalline solids have been developed in the fields of Solid State Physics and Crystallography. Thus, the need arose for expanding the realm of Physical Chemistry from its traditional concern with molecules and their properties and reactions to include the physics and chemistry of crystalline solids. This book deals with the applications of crystallography, group theory and thermodynamics to problems dealing with non­ molecular crystalline solids.