ABSTRACT
This diagram shows the unit cell of hexamethylbenzene translated 12 times. Ideally, these unit cells are repeated forever, covering the entire plane. In this chapter the concept of space group is introduced to study the organization of the symmetry operations when translations are included. In two dimensions these space groups may be informally called “wallpaper groups.” This chapter teaches the tools necessary to use the International Tables for Crystallography to interpret crystal structures.
