Demixing in two-dimensional anisotropic fluids

de las Heras, D.¹, Martínez-Ratón, Y.² and Velasco, E. ¹

¹Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Spain; ² Universidad Carlos III de Madrid, Spain

Hard anisotropic particles have played an important role as statistical mechanical models for liquid--crystal ordering. However, they are being used more recently to obtain liquid-crystal steady-state textures in vibrated monolayer experiments, where particles dissipate energy through inelastic collisions. In this communication we discuss some theoretical work, based on equilibrium statistical mechanics, which may help rationalise the steady-state textures observed in vibration experiments regarding their dependence with particle area fraction and mixture composition. One- and two-component particle mixtures are considered, and nematic ordering and demixing phenomena are analysed. Our focus is mainly on the isotropic and nematic phases, and specifically on an exotic variety of the latter, the so-called tetratic phase, possessing four-fold symmetry. We also present preliminary results of vibrated monolayer experiments, where two species of granular cylindrical particles of very different lengths exhibit strong demixing. Our theoretical work, based on equilibrium statistical mechanics, may help rationalise the steady-state textures observed in vibration experiments in terms of dependence on area fraction covered and mixture composition.