# THEORETICAL APPROACHES TO CALCULATION OF THERMODYNAMICS OF QUASIBINARY SEMICONDUCTOR SOLID SOLUTIONS

The review and analysis of theoretical approaches to the description of the thermodynamics of A3B5 and A2B6 type semiconductor solid solutions are presented. Phenomenological models existing at present are considered: the virtual crystal approximation; regular solution approximation of a; a subregular solution model; and the «delta-lattice-parameter» model. It is shown that in most cases the phenomenological methods are unsatisfactory. More perspective microscopic models of solid solution are analyzed: the simplest structural model with a tetrahedron as the main cluster; a model with larger clusters as the basic ones; a model of an infinite random solid solution in the form of a supercell with periodic boundary conditions. The main approaches for calculating the internal energy of the system are self-consistent first-principles calculations using the mechanism of functional density theory and the Martin-Keating’s approximation of valence force field. Theoretical methods for calculating the approximate expression for mixing entropy based on the quasi-chemical Guggenheim approximation and the Kikuchi’s variational method of clusters are also considered.

**Authors:** I. A. Cheremukhina

**Direction:** Physical Phenomena in a Solid Body, Liquids and Gases

**Keywords:** Solid solution, immiscibility gap,excess mixing free energy, mixing entropy,internal relaxation, main cluster, tetrahedral configuration, short-range-ordering correlation

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