Introduction to the theory of the solid state

Abstract

There have been many points in this book at which it has been apparent that the properties of aggregates of transition metal ions can differ from those of isolated molecules. This, in some measure, was a theme in the previous chapter and very much that of Chapter 15; it was met when discussing magnetic properties (Section 9.11), visible spectra (Section 8.11) and vibrational spectra (Sections 12.2.1 and 12.2.3). What, then, of the logical limit, the solid state? There has been an increasing interest in inorganic chemical aspects of the solid state in recent years, although it is a topic which is sometimes called material science. The subject covers the whole of the periodic table, not just transition metal species. Fortunately, the basic understanding and theory are common to all. It is the purpose of this chapter to give an introduction to this theory. Although it is a topic widely taught and studied, it seems the theory of the solid state is not always well understood by chemists. There are several reasons for this. First, crystalline materials have a great deal of symmetry, that of the translation operations that interrelate all the basic building blocks in the crystal (the term building blocks is preferred to molecules because not all crystals are molecular solids). The impact of group theory on chemistry is now so great that, given symmetry, chemists will look for the corresponding character table. Where, then, are the character tables appropriate to crystalline character lattices?