Hard-body models of bulk liquid crystals

TL;DR

This paper reviews hard-body models for anisotropic particles in bulk liquids, discussing their phase diagrams, theoretical approaches, and simulations, with a focus on liquid-crystal phase transitions and complex phase behaviors.

Contribution

It provides a comprehensive overview of hard particle models and their applications in understanding bulk liquid crystal phases and complex phase behaviors.

Findings

Complex phase diagrams including nematic, discotic, and ordered phases.

Mixtures exhibit demixing and orientational order competition.

Emphasis on equilibrium properties in simulations and theory.

Abstract

Hard models for particle interactions have played a crucial role in the understanding of the structure of condensed matter. In particular, they help to explain the formation of oriented phases in liquids made of anisotropic molecules or colloidal particles, and continue to be of great interest in the formulation of theories for liquids in bulk, near interfaces and in biophysical environments. Hard models of anisotropic particles give rise to complex phase diagrams, including uniaxial and biaxial nematic phases, discotic phases, and spatially ordered phases such as smectic, columnar or crystal. Also, their mixtures exhibit additional interesting behaviours where demixing competes with orientational order. Here we review the different models of hard particles used in the theory of bulk anisotropic liquids, leaving aside interfacial properties, and discuss the associated theoretical approaches and computer simulations, focusing on applications in equilibrium situations. The latter include one-component bulk fluids, mixtures and polydisperse fluids, both in two and three dimensions, and emphasis is put on liquid-crystal phase transitions and complex phase behaviour in general.