On the Theory of Isostructural Phase Transitions in Crystals

The thermodynamics of two types of isostructural phase transitions (IPT) is investigated in the framework of the Mitsui model using the molecular field approximation. The first type of IPT is obtained including four‐particle interaction members into the Hamiltonian. The consideration dealing with the temperature dependence of the asymmetry parameter explains IPT of the second type. It is shown that the maximum of dielectric constant may appear either in the point of IPT or above it. The investigation carried out gives a qualitative explanation of the experimental facts in numerous crystals undergoing IPT.