The constraints for the thermodynamic parameters of the (A,B)m(A,B)n↔(A,B)m+n type order-disorder transformation

A mathematical analysis of the constraints on the thermodynamic parameters of the compound energy formalism for an (A,B)m(A,B)n↔(A,B)m+n type order-disorder transformation is studied. Both the ordered phase and the disordered phase can be described using the two-sublattice model after the formula (AyA′ByB′)m(Aya″ByB″)n, with yi′=yi″(i=A,B) for the disordered phase and yi′≠yi″ for the ordered phase. The constraints between the parameters for the ordered state were derived. The thermodynamic characteristics of the transformation are illustrated using a mathematical method and the validity of the model and the constraints is tested.