ABSTRACT

Early in the history of modern science it was suggested that the regular external form of crystals (their morphology) implied an internal regularity. Visual inspection of many different crystals led to the realization that they all corresponded to one of only seven regular shapes called the seven crystal systems. Which system a crystal belongs to is determined by measuring the angles between its faces, and deciding how many axes are needed to de—ne the principal features of its shape. Figure 1.1 depicts the three crystallographic axes (a, b, c) and angles (α, β, γ) that de—ne the shape of a crystal. Notice how x, y, z do not necessarily correspond to a, b, c, except for a rectangular shape.