Mean-field theory of the uniaxial ferroelectric smectic A liquid crystal phase

TL;DR

This paper develops a mean-field molecular model to explain the phase behavior of ferroelectric smectic A liquid crystals and validates it with experimental measurements such as second harmonic generation and X-ray diffraction.

Contribution

It introduces a new mean-field model that accurately captures the phase diagrams of ferroelectric smectic A liquid crystals based on two parameters.

Findings

Model successfully reproduces experimental phase diagrams.

Experimental data confirms the model's predicted order parameters.

The study enhances understanding of ferroelectric smectic A phases.

Abstract

Following the groundbreaking discovery of the ferroelectric nematic liquid crystal phase (NF), a series of closely-related new polar phases have also been found. An especially interesting one is the ferroelectric smectic A phase (SmAF) with spontaneous polarization along the layer normal observed in a few materials of the NF realm. Here, we present a mean-field molecular model that successfully captures the rich phase diagrams experimentally observed in the literature in terms of two parameters. Additionally, we carry out second harmonic generation, X-ray diffraction and birefringence measurements in a compound exhibiting the SmAF phase to determine the appropriate order parameters and compare with the model predictions.