The isotropic-nematic interface in suspensions of hard rods: Mean-field properties and capillary waves

TL;DR

This study investigates the isotropic-nematic interface in hard spherocylinder suspensions, comparing Monte Carlo simulations with Onsager theory, and explores capillary wave anisotropy and elasticity effects.

Contribution

It combines simulation and theoretical analysis to characterize interfacial properties and capillary wave behavior in anisotropic particle suspensions, highlighting anisotropic spectra and rigidity effects.

Findings

Good agreement between Monte Carlo and Onsager theory for interfacial profiles.

Capillary wave spectrum is strongly anisotropic and quadratic at accessible wave-numbers.

Director field bending rigidity influences capillary wave behavior.

Abstract

We present a study of the isotropic-nematic interface in a system of hard spherocylinders. First we compare results from Monte Carlo simulations and Onsager density functional theory for the interfacial profiles of the orientational order parameter and the density. Those interfacial properties that are not affected by capillary waves are in good agreement, despite the fact that Onsager theory overestimates the coexistence densities. Then we show results of a Monte Carlo study of the capillary waves of the interface. In agreement with recent theoretical investigations (Eur.Phys.J. E {\bf 18} 407 (2005)) we find a strongly anistropic capillary wave spectrum. For the wave-numbers accessed in our simulations, the spectrum is quadratic, i.e.elasticity does not play a role. We conjecture that this effect is due to the strong bending rigidity of the director field in suspensions of spherocylinders.