Liquid crystal films on curved surfaces: An entropic sampling study

TL;DR

This study uses entropic sampling Monte Carlo simulations to explore how surface anchoring strength influences the isotropic-to-nematic phase transition in liquid crystal films on curved spherical surfaces, revealing a threshold effect and bistability.

Contribution

It introduces a high-precision entropic sampling approach to analyze the impact of surface anchoring on phase behavior in curved liquid crystal films, highlighting a threshold and bistability phenomena.

Findings

Identified a threshold anchoring strength separating uniaxial and radially ordered nematic phases.

Discovered bistable microstates near the threshold anchoring strength.

Demonstrated how surface anchoring modifies phase transition temperatures.

Abstract

The confining effect of a spherical substrate inducing anchoring (normal to the surface) of rod-like liquid crystal molecules contained in a thin film spread over it has been investigated with regard to possible changes in the nature of the isotropic-to-nematic phase transition as the sample is cooled. The focus of these Monte Carlo simulations is to study the competing effects of the homeotropic anchoring due to the surface inducing orientational ordering in the radial direction and the inherent uniaxial order promoted by the intermolecular interactions. By adopting entropic sampling procedure, we could investigate this transition with a high temperature precision, and we studied the effect of the surface anchoring strength on the phase diagram for a specifically chosen geometry. We find that there is a threshold anchoring strength of the surface below which uniaxial nematic phase results, and above which the isotropic fluid cools to a radially ordered nematic phase, besides of course expected changes in the phase transition temperature with the anchoring strength. In the vicinity of the threshold anchoring strength we observe a bistable region between these two structures, clearly brought out by the characteristics of the corresponding microstates constituting the entropic ensemble.