Question

Why does Frenkel defect not change the density of $AgCl$ crystals?

Answer 1

A Frenkel defect or Frenkel disorder is a type of point defect in a crystal lattice. The defect forms when an atom or smaller ion (usual cation) leaves its place in the lattice, creating a vacancy, and becomes an interstitial by lodging in a nearby location.

Frenkel defect does not change the density of AgCl crystals because in this defect, the Ag+ ions missing from the lattice sites occupy interstitial sites in the lattice thereby maintaining the stoichiometry of the crystal.