Phase behavior of a lattice-gas model for biaxial nematics

TL;DR

This study uses a lattice-gas model to analyze the phase behavior of biaxial nematic liquid crystals, revealing complex phase diagrams and critical points that enhance understanding of their microscopic interactions.

Contribution

It introduces a lattice-gas extension of the Maier--Saupe model for biaxial nematics, linking microscopic parameters to phenomenological Landau coefficients.

Findings

Identified stable biaxial and uniaxial nematic phases.

Mapped phase diagrams with various critical points.

Connected microscopic interactions to macroscopic phenomenology.

Abstract

We employ a lattice-gas extension of the Maier--Saupe model with discrete orientation states to study the phase behavior of a statistical model for biaxial nematogenic units in mean-field theory. The phase behavior of the system is investigated in terms of the strength of isotropic interaction between anisotropic objects, as well as the degree of biaxiality and the concentration of those units. We obtain phase diagrams with isotropic phases and stable biaxial and uniaxial nematic structures, various phase coexistences, many types of critical and multicritical behaviors, such as ordinary vapor-liquid critical points, critical end points and tricritical points, and distinct Landau-like multicritical points. Our results widen the possibilities of relating the phenomenological coefficients of the Landau--de Gennes expansion to microscopic parameters, allowing an improved interpretation of theoretical fittings to experimental data.