Defect Concentration in Ionic Compounds

In this section, we discuss the defect concentration of compounds that do not exhibit electronic conduction, such as pure NaCl. 

In thermal equilibrium, some ionic crystals at a temperature above absolute zero enclose a certain number of Schottky pair defects, that is, anion and cation vacancies in the structure (see Section 5.7.1) [13]. Since the concentration of Schottky pair defects at equilibrium at an absolute temperature, T, obeys the mass action law, then [16] 

Cv is the equilibrium concentration of anion vacancies Cv is the total concentration of cation vacancies 

AGschottky represents the Gibbs free energy of formation of the vacancy pair 

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