Cluster Formation and Percolation in Ethanol-Water mixtures

TL;DR

This study uses molecular dynamics simulations to analyze cluster formation and percolation in ethanol-water mixtures, revealing percolation thresholds and fractal dimensions across concentrations, aligning with experimental thermodynamic data.

Contribution

It provides detailed percolation analysis in ethanol-water mixtures using multiple hydrogen bond definitions, expanding understanding of cluster behavior across compositions.

Findings

All mixtures are above the 3D percolation threshold.

Water percolation occurs in mixtures with less than 40 mol % ethanol.

Fractal dimensions range from 2.53 to 2.9 depending on concentration.

Abstract

Results of systematic molecular dynamics studies of ethanol-water mixtures, over the entire concentration range, were reported previously to agree with experimental X-ray diffraction data. These simulated systems are analyzed in this work to examine cluster formation and percolation, using four different hydrogen bond definitions. Percolation analyses revealed that each mixture (even the one containing 80 mol % ethanol) is above the 3D percolation threshold, with fractal dimensions, df, between 2.6 to 2.9, depending on concentration. Monotype water cluster formation was also studied in the mixtures: 3D water percolation can be found in systems with less than 40 mol % ethanol, with fractal dimensions between 2.53 and 2.84. These observations can be put in parallel with experimental data on some thermodynamic quantities, such as the excess partial molar enthalpy and entropy.