The restricted primitive model of ionic fluids with nonadditive diameters

TL;DR

This paper investigates how nonadditive diameters in the restricted primitive model of ionic fluids influence clustering behavior and phase separation, revealing distinct effects for positive and negative nonadditivity.

Contribution

It provides accurate cluster concentration calculations and explores the impact of nonadditivity on clustering and gas-liquid coexistence using efficient Monte Carlo algorithms.

Findings

Negative nonadditivity leads to even-numbered, neutral clusters.

Positive nonadditivity promotes percolating clusters at high densities.

Nonadditivity significantly alters clustering and phase behavior.

Abstract

The restricted primitive model with nonadditive hard-sphere diameters is shown to have interesting and peculiar clustering properties. We report accurate calculations of the cluster concentrations. Implementing efficient and ad hoc Monte Carlo algorithms we determine the effect of nonadditivity on both the clustering and the gas-liquid binodal. For negative nonadditivity, tending to the extreme case of completely overlapping unlike ions, the prevailing clusters are made of an even number of particles having zero total charge. For positive nonadditivity, the frustrated tendency to segregation of like particles and the reduced space available to the ions favors percolating clusters at high densities.