When AgCl is doped with CdCl₂ a cation vacancy defect is created i.e. An Ag⁺ ion from the lattice is absent its position due to presence of adjacent Cd⁺⁺ ion.

 Na₂O is the solid in which cation occupy all the tetrahedral voids. in Na₂O, Na⁺ ion is surrounded by four oxide ion and oxide ion surrounded by the eight sodium ion.

Frenkel defect tends to increase the dielectric constant of the crystal. Compounds having such defect conduct electricity to a small extent. When electric field is applied, an ion moves from its lattice site to occupy a hole, it creates a new hole. In this way, a hole moves from one end to the other. Thus, it conducts electricity across the crystal. Due to the presence of holes, stability (or the lattice energy) of the crystal decreases.

If F-centres are introduced into a transparent crystal lattice then they will induce colour into the materiale for example NaCl heated in sodium vapours the crystal becomes coloured.