Phase separation of binary systems

Abstract

In this paper, three physical predictions on the phase separation of binary systems are derived based on a dynamic transition theory developed recently by the authors. First, the order of phase transitions is precisely determined by the sign of a nondimensional parameter K such that if K > 0 , the transition is first order with latent heat and if K < 0 , the transition is second order. Here the parameter K is defined in terms of the coefficients in the quadratic and cubic nonlinear terms of the Cahn–Hilliard equation and the typical length scale of the container. Second, a phase diagram is derived, characterizing the order of phase transitions, and leading in particular to a prediction that there is only a second-order transition for molar fraction near 1 / 2 . This is different from the prediction made by the classical phase diagram. Third, a T L -phase diagram is derived, characterizing the regions of both homogeneous and separation phases and their transitions.