Question

What type of defect is shown in the given crystal lattice?

• A. Frenkel defect
• B. Schottky defect
• C. Metal excess defect
• D. Metal deficiency defect

Answer 1

The correct option is A Frenkel defect

In the given crystal lattice, cation $A^{+}$ after leaving its lattice site has occupied a position at an interstitial site.
Also, the charge is neutral since the positive ion is delocalised in the lattice and it has not left the lattice.
Also, there are no ion(s) with different valencies.
Here, only $A^{+}$ ion is delocalised to the interstitial site. Hence, it shows Frenkel defect.

Characteristics of Frenkel defect:
1. It occurs in ionic crystals which have a large difference in size between the positive and negative ions.
2. The coordination number of ionic crystal is usually low (4 or 6).
3. Density of the crystal doesn’t change.
4. $ZnS,AgCl,AgBr\&AgI$ shows Frenkel defects.