Fluids of rod-like particles near curved surfaces

TL;DR

This paper investigates how fluids of hard, rod-like particles behave near curved surfaces, revealing non-analytic surface tension behavior at low densities and the impact of interactions on this property.

Contribution

It provides a detailed analysis of density, orientation, and surface tension profiles of rod-like particles near curved surfaces using the Onsager approximation, highlighting non-analytic behavior.

Findings

Surface tension $\gamma(R)$ is non-analytic at $1/R=0$ in the low-density limit.

Interparticle interactions alter the behavior of $\gamma(R)$ compared to the non-interacting case.

The Onsager approximation effectively computes profiles and surface tension for curved surfaces.

Abstract

We study fluids of hard rods in the vicinity of hard spherical and cylindrical surfaces at densities below the isotropic-nematic transition. The Onsager second virial approximation is applied, which is known to yield exact results for the bulk properties in the limit of infinitely thin rods. This approach requires the computation of the one-particle distribution function and of the Mayer function which is greatly facilitated by an appropriate expansion in terms of spherical harmonics. We determine density and orientational profiles as well as the surface tension $\gamma$ as function of the surface curvature radius $R$. Already in the low-density limit of non-interacting rods $\gamma(R)$ turns out to be non-analytic at $1/R=0$, which prohibits the application of the commonly used Helfrich expansion. The interparticle interaction modifies the behavior of $\gamma(R)$ as compared to the low-density limit quantitatively and qualitatively.