Z

FCC sublattices

, one being occupied by the Zn atoms and the other by the S atoms. The sublattices are shifted by 1/4

〈

〉

with respect to one another (see Figure Z.1). Another way of describing the structure is the following: the S atoms form an FCC sublattice in which the Zn atoms form the other sublattice, whose sites occupy one half of the

tetrahedral voids

in the first one. A

coordination polyhedron

for both of the atom types in the structure is a tetrahedron, which implies that the

covalent crystals

with tetragonal

bond directionality may have the same structure. This is the case, e.g., in III-V semiconductor compounds.