Question

What is the new location of a smaller ion in the Frenkel defect?

Answer 1

Hint: Crystal defects or solid defects are the absence of atoms or ions in an ideal or imaginary crystal arrangement or lattice and the misalignment of unit cells in particular crystals.

Complete answer:
A Frenkel defect is a crystalline solid point defect named after its discoverer, Yakov Frenkel. The Frenkel defect (also known as the Frenkel pair or disorder) is a lattice crystal defect in which an atom or ion occupies a normally empty site that is not it's own. As a consequence, the atom or ion own lattice site is left vacant.
When an atom or smaller ion (usually a cation) leaves its position in the lattice, a vacancy is created, and the defect forms by settling in a nearby position. As Frenkel defects forming enthalpy are usually far higher than that of other point defects, they are mainly produced during particle irradiation in elemental systems, such as vacancies, and their equilibrium concentration according to the Boltzmann distribution is below the detection limit.
Frenkel defect may also occur naturally in ionic crystals with a less coordination number or a large difference in the sizes of the ions, where the smaller ion (usually the cation) is dislocated.
Therefore, in the Frenkel defect, the smaller ion is dislocated from its normal site to the interstitial site (vacant site).

Note:
Point defects are made up of a single atom or a small cluster of atoms and are classified into two types: vacancies where an atom (or, in an ionic material, an atom pair) is missing and interstitials where the extra atom is located in a usually unoccupied structural site.