Frenkel defect

A Frenkel defect is a type of imperfection in a crystal structure where an ion, usually a cation (positively charged ion), temporarily leaves its regular spot in the crystal lattice and moves into an empty space or vacancy nearby. This creates a paired defect: a vacancy where the ion used to be and an interstitial site occupied by the ion. The overall composition stays the same, but locally the arrangement is disturbed. Frenkel defects commonly occur in ionic crystals with a large difference between ion sizes, like silver chloride or zinc sulfide, and can influence the material’s properties such as conductivity.