Oxide Crystal Structures

In Chapter 10 it was shown that silicate structures use the cation (silicon) as the reference point and develop anion (oxygen) polyhedrons around the cation. Oxide structures, excluding silica, can be represented by using the anion as the reference position. The simpler oxide structures can be considered as close packed spheres of oxygen and their interstitial sites, which can be occupied by cations. These close packed systems include the body-centered cubic (BCC), face-centered cubic (FCC), and hexagonal close packed (HCP). The FCC and HCP have the same packing arrangement, as shown in Figure 12-1. Note the hexagon obtained by drawing lines from the center of the neighboring anions.