The symmetry properties of molecules were discussed in Chapter 6, and the corresponding properties of crystals are presented here. In contrast to discrete molecules, crystals have a lattice structure with three-dimensional periodicity. Hence, additional symmetry elements such as translations, screw axes, and glide planes, which are applicable to an infinitely extended system, need to be considered. This chapter introduces the concept and nomenclature of space groups and their application in describing the structures of crystals. Examples of crystal structures for selected space groups are provided. The chapter concludes with a section on the use of space group symmetry in the determination of crystal structure. In short, the chapter gives a succinct introduction to the symmetry of crystals.
Keywords: asymmetric unit, Bravais lattices, crystal classes, equivalent positions, fractional coordinates, glide plane, Miller indices, Hermann-Mauguin notation, screw axis, space groups