Statistical mechanics of bend flexoelectricity and the twist-bend phase in bent-core liquid crystals

TL;DR

This paper develops a Landau theory for bend flexoelectricity in bent-core liquid crystals, predicting a phase transition to a nonuniform polar phase, and validates it with Monte Carlo simulations.

Contribution

It introduces a Landau theoretical framework for bend flexoelectricity and confirms its predictions through Monte Carlo simulations.

Findings

Flexoelectric coefficient increases near the phase transition.

A second order transition to a nonuniform polar phase occurs.

Simulations support the theoretical predictions.

Abstract

We develop a Landau theory for bend flexoelectricity in liquid crystals of bent-core molecules. In the nematic phase of the model, the bend flexoelectric coefficient increases as we reduce the temperature toward the nematic to polar phase transition. At this critical point, there is a second order transition from high-temperature uniform nematic phase to low-temperature nonuniform polar phase composed of twist-bend or splay-bend deformations. To test the predictions of Landau theory, we perform Monte Carlo simulations to find the director and polarization configurations as functions of temperature, applied electric field, and interaction parameters.