Cations are present in the interstitial sites in …………… .

Options

A. Frenkel defect
B. Schottky defect
C. Vacancy defect
D. metal deficiency defect

Explanation

To solve the question "Cations are present in the interstitial sites in ……………," we need to analyze the options provided and understand the types of defects in solid-state chemistry.

### Step-by-Step Solution:

1. **Understanding Interstitial Sites**:
- Interstitial sites are the spaces between the atoms in a crystal lattice where smaller ions (cations) can fit.

2. **Identifying the Defects**:
- **Frenkel Defect**: This defect occurs when a cation leaves its original lattice position and occupies an interstitial site, creating a vacancy.
- **Schottky Defect**: This defect involves the simultaneous absence of equal numbers of cations and anions from their lattice sites, leading to vacancies but not interstitial occupancy.
- **Frequency Defect**: This term is not standard in solid-state chemistry and is likely a distractor.
- **Metal Deficiency Defect**: This defect refers to a situation where there is a lower amount of metal ions than expected in the compound, but it does not specifically relate to interstitial sites.

3. **Conclusion**:
- Based on the definitions, the correct answer is that cations are present in the interstitial sites in a **Frenkel defect**.

Thus, the final answer is:
**Cations are present in the interstitial sites in Frenkel defect.**