Equilibrium Concentration of Schottky Defects Derived from Configurational Entropy

1 Equilibrium Concentration of Schottky Defects Derived from Configurational Entropy 

The introduction of Schottky defects causes the Gibbs energy of the crystal to change by an amount AGs  

In a crystal of overall composition MX, suppose that ns is the number of Schottky defects in the crystal at a temperature T (K), that is, there are ns vacant cation sites and ns vacant anion sites present, distributed over N possible cation sites and N possible anion sites. The configurational entropy change, ASs, due to the distribution of the 

The total number of ways of distributing these defects, W, is given by the product of wc and wa, hence  

Therefore, the change in configurational entropy caused by introducing these defects is 

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