(563c) Structure of Rigid Hard-Ring Fluid

The structure of hard ring fluids is studied in two and three dimensions, using Monte Carlo computer simulations in the canonical ensemble. These fluids are composed of molecules consisting of hard-spheres linked together to form planar rigid rings. For rings of various sizes and for a wide range of densities, results are reported for the pair distribution function of the ring centers and for the pair distribution of the ring orientations. In a dense monolayer, where the rings are completely confined to a plane, a "shoulder", precursor of the freezing transition, is observed in the second peak of the pair distribution function of the ring centers, as previously seen in the simple hard-sphere fluid. In two dimensions, where the ring centers are confined to a plane but the rings themselves are free to rotate on all axes, nematic and tetratic ordering is observed at sufficiently high densities. Results are also presented for three dimensions.