In cubic ZnS,the radii of the Znand S atoms are 0.83Ao and 1.74 Ao respectively. What is the edge length of the unit cell of ZnS?
2.57 Ao
3.64 Ao
2.97 Ao
5.935 Ao
This figure shows one part of eight cubic components of a unit cell of ZnS.
Let edge length of the unit cell = a
3×a2×12=rZn2++rS2−
or 3a4=0.83+1.74=2.57
or a=2.57×43=5.935Å