Phase Behavior of Binary Fluid Mixtures Confined in a Model Aerogel

TL;DR

This study uses Monte-Carlo simulations with a fractal gel model to analyze the phase behavior of binary fluid mixtures in aerogel, revealing narrowed coexistence regions and metastable states similar to experimental observations.

Contribution

Introduces a Monte-Carlo simulation approach with a fractal gel model to study phase diagrams of confined binary mixtures, aligning with experimental results and exploring metastable states.

Findings

Coexistence region is substantially narrowed in aerogel confinement.

Phase diagram qualitatively matches experimental data.

Metastable branches are observed, not yet seen experimentally.

Abstract

It is found experimentally that the coexistence region of a vapor-liquid system or a binary mixture is substantially narrowed when the fluid is confined in a aerogel with a high degree of porosity (e.g. of the order of 95% to 99%). A Hamiltonian model for this system has recently been introduced (J.Donley PRE 55:539, 1997}. We have performed Monte-Carlo simulations for this model to obtain the phase diagram for the model. We use a periodic fractal structure constructed by diffusion-limited cluster-cluster aggregation (DLCA) method to simulate a realistic gel environment. The phase diagram obtained is qualitatively similar to that observed experimentally. We also have observed some metastable branches in the phase diagram which have not been seen in experiments yet. These branches, however, might be important in the context of recent theoretical predictions and other simulations.