ИСТИНА

Thermodynamic modeling plays a significant role in the study of phase diagrams of multicomponent systems. The quality of predicting thermodynamic properties and phase equilibria in multicomponent systems depends on the reliability and methods of describing boundary subsystems. The Redlich-Kister-Muggianu (RKM) polynomials is widely used to describe disordered ternary phases. However, thermodynamic modeling of systems with strong short-range order (SRO) using the RKM model is often difficult. The literature indicates that other models may be more effective for such systems: the associated solution (AS) model or a modified quasi-physical model. In this work, using the example of ternary systems (Ag, In)–Pd–Sn with strong short-range order, the effectiveness of the RKM and AS models in describing the properties of the melt was compared. The thermodynamic properties of the melt of ternary systems (Ag, In)–Pd–Sn were calculated using the RKM and AS models. The corresponding thermodynamic descriptions of the Pd-Sn binary were accepted from [1]. It is found that without ternary interactions in both ternary systems, the associated solutions model reproduces the literature experimental data on component activities and enthalpy of formation much better. Fig. 1 shows a comparison of the calculated enthalpies of melt formation with experimental data [2, 3]. In the In–Pd–Sn, the RKM model showed comparable results with ternary interactions, but it should be noted that the ternary parameters had high modulus values. In the case of the Ag–Pd–Sn system, using the RKM model with ternary interactions, it was not possible to obtain a consistent description of the thermodynamic properties of the melt and phase boundaries, and spurious miscibility gaps appeared.