Pattern formation in binary fluid mixtures induced by short-range competing interactions

TL;DR

This study uses simulations and theoretical calculations to explore pattern formation in binary fluids with competing short-range interactions, revealing microheterogeneity driven by depletion forces and enhanced by ionic charges.

Contribution

It demonstrates how short-range attractive and long-range repulsive interactions lead to pattern formation, including effects of ionic charges, in a simplified molecular model.

Findings

Pattern formation driven by depletion forces observed.

Effective potentials show short-range attraction and long-range repulsion.

Inclusion of charges enhances intermediate range order.

Abstract

Molecular dynamics simulations and integral equation calculations of a simple equimolar mixture of diatomic molecules and monomers interacting via attractive and repulsive short-range potentials show the existence of pattern formation (microheterogeneity), mostly due to depletion forces away from the demixing region. Effective site-site potentials extracted from the pair correlation functions using an inverse Monte Carlo approach and an integral equation inversion procedure exhibit the features characteristic of a short-range attractive and long-range repulsive potential. When charges are incorporated into the model, this becomes a coarse grained representation of a room temperature ionic liquid, and as expected, intermediate range order becomes more pronounced and stable.