Critical end point behaviour in a binary fluid mixture

TL;DR

This paper investigates the critical end point behavior in a binary fluid mixture, demonstrating through scaling arguments and Monte Carlo simulations that the coexistence curve diameter exhibits singular behavior near the critical end point, with implications for experimental detection.

Contribution

The study provides the first combined theoretical and simulation evidence for singular behavior in the coexistence diameter near the critical end point in binary fluids.

Findings

Evidence of singularity in the coexistence diameter

Confirmation of singularity in coexistence chemical potential

Simulation results align with theoretical predictions

Abstract

We consider the liquid-gas phase boundary in a binary fluid mixture near its critical end point. Using general scaling arguments we show that the diameter of the liquid-gas coexistence curve exhibits singular behaviour as the critical end point is approached. This prediction is tested by means of extensive Monte-Carlo simulations of a symmetrical Lennard-Jones binary mixture within the grand canonical ensemble. The simulation results show clear evidence for the proposed singularity, as well as confirming a previously predicted singularity in the coexistence chemical potential [Fisher and Upton, Phys. Rev. Lett. 65, 2402 (1990)]. The results suggest that the observed singularities, particularly that in the coexistence diameter, should also be detectable experimentally.