Zinc Blende crystal structure

The zinc blende crystal structure is the structure named for the low-temperature phase of the ceramic ZnS. It is cubic with two interpenetrating FCC lattices. One at the normal position and one at (1/4,1/4,1/4). Another way to think of it is an FCC lattice with half of its tetrahedral interstitials filled. The structure has 8 atoms per unit cell (4 formula units of ZnS). The lattice parameter can be found by noticing that atoms touch along body diagonal. 1/4*sqrt(d)*a=R_cation+R_anion. The compound has another phase, wurtzite, that is hexagonal and stable at high-temperature.