Why is the Frenkel defect not found in pure alkali metal halides?

Frenkel defect is noticed in:

Discuss Frenkel defect.

Which non-stoichiometric point defect is responsible for colour in alkali metal halides?

Which type of defect is found in thalassemia?

Lithium is the strongest reducing agent among the alkali metals due to the following factor.

In the case of the alkali metals:

Why does Frenkel defect not change the density of AgCl crystal?