Generalization of the Maier-Saupe theory to the ferroelectric nematic phase

TL;DR

This paper extends the classical Maier-Saupe theory to include ferroelectric nematic phases by adding a polar term, allowing for better understanding of phase transitions and properties of ferroelectric nematics.

Contribution

The paper introduces a natural generalization of the Maier-Saupe theory to describe ferroelectric nematic phases, incorporating polar order parameters and phase transition behaviors.

Findings

The theory predicts first-order phase transitions with or without intermediate nematic phases.

Temperature dependence of polar and nonpolar order parameters matches some experimental data.

The generalized model provides a first approximation for ferroelectric nematic properties.

Abstract

We present a generalization of the Maier-Saupe (MS) theory that incorporates the description of the ferroelectric nematic phase (NF) within its scope of application. The extension of the theory is carried out in a natural way, by adding to the nematic potential of MS a term proportional to cos{\theta} and to the polar order parameter <cos{\theta} >, where {\theta} is the angle between the long molecular axis and the spontaneous polarization. The NF phase can be reached by cooling from the isotropic phase with or without the formation of an intermediate normal nematic phase, depending on the relative intensity of the polar and nonpolar terms of the nematic potential. For both phase sequences all the transitions are first order. The temperature dependence of the polar and nonpolar order parameters is calculated, and some results derived from the theory are compared with the experimental observations. It is argued that the theory is a valuable first approximation to describe some of the properties of ferroelectric nematics.