Clustering in complex ionic liquids in two dimensions

TL;DR

This study uses simulations and integral equations to analyze how reduced dimensionality and neutral sites affect ionic liquid clustering and phase behavior, revealing suppression of liquid-gas transition and emergence of bilayer ordering.

Contribution

It introduces a comparative analysis of 2D ionic liquids with neutral sites versus 3D models, highlighting the impact on phase transitions and structural correlations.

Findings

Neutral site addition suppresses liquid-gas transition.

Bilayer membrane ordering occurs at low temperatures.

Theoretical predictions align well with simulations until near the no-solution region.

Abstract

Two-dimensional ionic liquids with single site anion and cation-neutral dimer are studied by computer simulations and integral equation techniques, with the aim of characterizing differences with single site anion-cation mixtures, and also with three dimensional equivalents of both models, in order to see the competition between the Coulomb interactions and the clustering restrictions due to reduced dimension. We find that the addition of the neutral site to the cation suppresses the liquid-gas transition which occurs in the case of the monomeric Coulomb system. Instead, bilayer membrane type ordering is found at low temperatures. The agreement between the structural correlations predicted by theory and the simulation is excellent until very close to the no-solution region predicted by the theory. These findings suggest various relations between the nature of the clustering at low temperatures, and the inability of the theory to enter this region