Question

In zinc blende structure, anions are arranged in ccp and cations are present in the tetrahedral voids and only half the tetrahedral voids are occupied.
If 'a' is the edge length of the unit cell, then for zinc blende structure the distance of closest approach between cation and anion is :

• A. $\frac{\sqrt{2}a}{2}$
• B. $\frac{\sqrt{3}a}{2}$
• C. $\frac{\sqrt{2}a}{4}$
• D. $\frac{\sqrt{3}a}{4}$

Answer 1

The correct option is D $\frac{\sqrt{3}a}{4}$

In ZnS structure along one body diagonal, we will find one cation and an anion touching each other.
Cation is present at the middle of the distance from the center to corner as it is a tetrahedral void position.
Therefore distance of closest approach $=\frac{\sqrt{3}\times a}{4}$