Multicomponent fluid of nonadditive hard spheres near a wall

TL;DR

This paper applies a rational-function approximation to analytically evaluate local density profiles of multicomponent nonadditive hard-sphere mixtures near a wall, comparing results with Monte Carlo simulations.

Contribution

It extends the rational-function approximation to multicomponent nonadditive hard-sphere mixtures near walls and assesses its accuracy against simulations.

Findings

The theory underestimates local densities at contact, especially for larger spheres.

It accurately captures the initial decay and oscillations of density profiles.

Good agreement with simulations for the decay behavior of densities.

Abstract

A recently proposed rational-function approximation [Phys. Rev. E \textbf{84}, 041201 (2011)] for the structural properties of nonadditive hard spheres is applied to evaluate analytically (in Laplace space) the local density profiles of multicomponent nonadditive hard-sphere mixtures near a planar nonadditive hard wall. The theory is assessed by comparison with $NVT$ Monte Carlo simulations of binary mixtures with a size ratio 1:3 in three possible scenarios: a mixture with either positive or negative nonadditivity near an additive wall, an additive mixture with a nonadditive wall, and a nonadditive mixture with a nonadditive wall. It is observed that, while the theory tends to underestimate the local densities at contact (especially in the case of the big spheres) it captures very well the initial decay of the densities with increasing separation from the wall and the subsequent oscillations.