Stability of the Liquid Phase in Colloidal Electrolytes

TL;DR

This study uses Monte Carlo simulations to analyze the phase diagram of charged colloids, revealing stable liquid phases and different crystal structures depending on temperature, with implications for understanding colloidal electrolyte behavior.

Contribution

It provides the first detailed phase diagram of a colloidal electrolyte modeled with DLVO potential, highlighting liquid stability and crystal coexistence phenomena.

Findings

Liquid-gas first order transition similar to ionic fluids.

High T crystallizes in FCC lattice, low T in coexistence with BCC crystal.

Gas-liquid stability region narrows with reduced interaction range.

Abstract

The equilibrium phase diagram of a 1:1 symmetrical mixture composed of oppositely charged colloids is calculated using Monte Carlo simulations. We model the system by the DLVO effective interaction potential. The phase diagram is similar to that of its atomic analog (the ionic fluid), where a liquid-gas first order transition emerges in the low $T-\rho$ regions being stable with respect to crystallization. As in the ionic fluids, we have found two different crystals: at high $T$ the fluid crystallizes in a FCC lattice, whereas at low $T$, the liquid coexists with a BCC crystal. The region of gas-liquid stability is observed to be narrower as the interaction range is diminished.