In a crystal, Frenkel defect is not shown by alkali metal halides but silver halides show. Why ?

Explanation

To understand why Frenkel defects are not shown by alkali metal halides but are present in silver halides, we need to analyze the nature of these compounds and the characteristics of Frenkel defects.

### Step-by-Step Solution:

1. **Definition of Frenkel Defect**:
- A Frenkel defect is a type of point defect in a crystal lattice where an atom or ion is displaced from its normal lattice position to an interstitial site, creating a vacancy at the original site.

2. **Characteristics of Alkali Metal Halides**:
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