Phase behavior of hard circular arcs

By using Monte Carlo numerical simulation, this work investigates the phase behavior of systems of hard thin circular arcs, from an aperture angle θ → 0 to an aperture angle θ → 2π, in the twodimensional Euclidean space. Except in the isotropic phase at lower density and in the (quasi) nematic phase, the other phases that form, including the isotropic phase at higher density, hard infinitesimally thin circular autoassemble to form clusters. These clusters are either filamentous, for smaller values of θ, or roundish, larger values of θ. Provided the density is sufficiently high, the filaments lengthen, merge, and straighten finally produce a filamentary phase while the roundels compact and dispose themselves with their centers of at the sites of a triangular lattice to finally produce a cluster hexagonal phase