Temperature dependent dynamics in water-ethanol liquid mixtures

TL;DR

This study investigates how temperature affects hydrogen bonding and molecular dynamics in water-ethanol mixtures with varying ethanol concentrations, revealing changes in interaction energies, diffusion barriers, and reorientational times.

Contribution

It provides detailed insights into the temperature-dependent dynamical behavior and hydrogen bond energetics in water-ethanol mixtures across different concentrations.

Findings

Water-water interactions strengthen with temperature.

Ethanol-ethanol interactions weaken in mixtures.

Reorientational times increase with ethanol concentration.

Abstract

Temperature dependent hydrogen bond energetics and dynamical features, such as the diffusion coefficient and reorientational times, have been determined for ethanol-water mixtures with 10, 20 and 30 mol % of ethanol. Concerning pairwise interaction energies between molecules, it is found that water-water interactions become stronger, while ethanol-ethanol ones become significantly weaker in the mixtures than the corresponding values characteristic to the pure substances. Concerning the diffusion processes, for all concentrations the activation barrier of water and ethanol molecule become very similar to each other. Reorientation motions of water and ethanol become slower as ethanol concentration is increasing. Characteristic reorientational times of water in the mixtures are substantially longer than these values in the pure substance. On the other hand, this change for ethanol is only moderate. The reorientation motions of water (especially the ones related to the H-bonded interaction) become very similar for those of ethanol in the mixtures.