What is the crystal defect called when in a solid lattice, the cation…

The crystal defect called when in a solid lattice, the cation has left a lattice site and is located at interstitial position is 1. Frenkel defect.

In a Frenkel defect, an atom or ion leaves its regular lattice site and occupies an interstitial position, creating a vacancy at the original lattice site. This defect is common in crystals with large ions, such as silver halides.

The other three options are incorrect.

2. A Schottky defect is a vacancy defect in which equal numbers of cations and anions are missing from their lattice sites.

3. An interstitial defect is a defect in which an atom or ion occupies an interstitial position, which is a space between regular lattice sites.

4. A positive particle excess defect is a defect in which there are more positive ions than negative ions in the crystal.