Asymmetrical disorders in stoichiometric binary solids

In an asymmetrical disorder, the two defects that make it up pertain to the same sub-lattice of A or of B. In practice, we find only two families of anti-S5mmetrical disorders Frenkel disorder and so-called AS disorder. 

Frenkel disorder is the simultaneous presence of vacancies and interstitials of the same element. Thus, we have two possible Frenkel disorders for a binary system Frenkel disorder on the element A and on the element B. Frenkel disorder is essentially foxmd if there is a significant difference between the dimensions of the atoms of A and those of the atoms of B. It is for the smallest element (so as to accommodate the small atom in an interstitial position in the cavities left by the sub-lattice of the largest) that the Frenkel disorder is most 

Let us choose Frenkel disorder on A. Regardless of the values of the numbers m and n, the formation reaction is written as  

The disorder does not alter the stoichiometry of sites, so the expression of the law of mass action does not involve the coefficients m and n. The equilibrium constant A) (a) depends on the temperature by the standard enthalpy of formation.  

The AS disorder is characterized by the simultaneous presence of vacancies and exchanged atoms of the same nature. Thus, we will have two possibilities of AS disorder either on the sublattice of A with the defects Va and Ab, or on the sublattice of B with the defects Vb and Ba. The equilibrium of formation of disorder is written as  

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