Potential of Mean Force between a Spherical Particle Suspended in a Nematic Liquid Crystal and a Substrate

TL;DR

This paper investigates the liquid-crystal mediated potential of mean force between a spherical particle and a substrate in a nematic liquid crystal system using advanced Monte Carlo simulation techniques, revealing an attractive interaction.

Contribution

It introduces a novel simulation method combining expanded ensemble and density of states formalism to efficiently compute the potential of mean force.

Findings

Sphere is attracted to the surface without attractive molecular interactions

New simulation approach improves sampling efficiency

Potential of mean force varies with distance from the surface

Abstract

We consider a system where a spherical particle is suspended in a nematic liquid crystal confined between two walls. We calculate the liquid-crystal mediated potential of mean force between the sphere and a substrate by means of Monte Carlo simulations. Three methods are used: a traditional Monte Carlo approach, umbrella sampling, and a novel technique that combines canonical expanded ensemble simulations with a recently proposed density of states formalism. The latter method offers clear advantages in that it ensures good sampling of phase space without prior knowledge of the energy landscape of the system. The resulting potential of mean force, computed as a function of the normal distance between the sphere and a surface, suggests that the sphere is attracted to the surface, even in the absence of attractive molecular interactions.