Phase behavior of disklike hard-core mesogens

We report a computer-simulation study of a system of ``hard cut spheres,'' oblate particles that are obtained by slicing off the top and bottom caps of a sphere at a distance L/2 from the equatorial plane. This system serves as a model for a disklike mesogen. The phase behavior of this system is found to be strongly dependent on the length-to-width ratio (L/D) of the particles. In addition to isotropic and solid phases, we find nematic and columnar phases for L/D=0.1. For L/D=0.2 we find a columnar phase, and a phase with cubic orientational order but no translational order. For L/D=0.3, only the isotropic fluid and the solid are stable. Where possible, we have located the phase transitions.