Introduction

Solid state chemistry deals with a variety of solids, inorganic as well as organic; the solids can be crystalline or noncrystalline. A sound knowledge of the structure of solids as well as of the nature of bonding is essential for an appreciation of solid state chemistry since properties of solids are, by and large, determined by the structure. Crystal chemistry of inorganic solids has been reviewed widely in the literature (see, for example, Adams, 1974; Rao, 1974; Wells, 1984), but there has been effort of late to explore new ways of looking at inorganic structures and to understand their stabilities. In this chapter, we shall briefly review the highlights of inorganic crystal chemistry after summarizing some of the basic information related to crystals and the different types of bonding found in them. We shall also discuss polytypism, organic crystal structures and related topics before finally presenting the models employed to understand the structures of noncrystalline or amorphous solids.

Description of crystals

A regular crystal consists of an infinite array of constituent units in three dimensions. Since the nature of the constituent unit does not affect translational periodicity, the periodicity is generally represented by replacing the repeating unit by a point, the resulting array of such points in space being called a lattice. In a space lattice, the translation vectors a, b and c in the three crystallographic directions define a parallelepiped called a primitive cell.