Topological defects in nematic droplets of hard spherocylinders

Using computer simulations we investigate the microscopic structure of the singular director field within a nematic droplet. As a theoretical model fo r nematic liquid crystals we take hard spherocylinders. To induce an overal l topological charge, the particles are either confined to a two-dimensiona l circular cavity with homeotropic boundary or to the surface of a three-di mensional sphere. Both systems exhibit half-integer topological point defec ts. The isotropic defect core has a radius of the order of one particle len gth and is surrounded by free-standing density oscillations. The effective interaction between two defects is investigated. All results should be expe rimentally observable in thin sheets of colloidal liquid crystals.