THE WURTIZE STRUCTURES (ZnS):

It is an alternate form in which ZnS occurs in nature. The main features of this structure are

                                    A unit cell representation of wurtzite structure

(1) Sulphide ions have HCP arrangement and zinc ions occupy tetrahedral voids.

(2)  Only half the alternate tetrahedral voids are occupied by Zn⁺² ions.

(3)  Coordinate no. of Zn⁺² ions as well as S^-2 ions is 4. Thus, this structure has 4 : 4 coordination.

(4)  No. of Zn⁺² ions per unit cell: 

                                 = 4(within the unit cell) ´1 + 6(at edge centres) ´1/3  = 6

(5) No. of S^-2 ions per unit cell =

                                 = 12(at corners) ´1/6 +2 (at face centres) ½ +3 (within the unit cell)1=6

                            Thus, there are 6 formula units per unit cell.