Phase Separation of Binary Systems

TL;DR

This paper uses a dynamic transition theory to predict phase separation behaviors in binary systems, including transition order, a new transition diagram, and a critical length scale for phase separation.

Contribution

The authors derive three physical predictions on phase separation using a recently developed dynamic transition theory, providing new insights into transition order and size effects.

Findings

Transition order depends on the sign of parameter Kd.

Derived a new transition diagram predicting only second-order transitions near molar fraction 1/2.

Identified a critical length scale below which no phase separation occurs.

Abstract

In this Letter, 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 parameter Kd (or a nondimensional parameter K) such that if Kd>0, the transition is first-order with latent heat and if Kd <0, the transition is second-order. Second, a theoretical transition diagram is derived, leading in particular to a prediction that there is only second-order transition for molar fraction near 1/2. This is different from the prediction made by the classical transition diagram. Third, a critical length scale is derived such that no phase separation occurs at any temperature if the length of the container is smaller than the critical length scale.