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 for nematic liquid crystals we take hard spherocylinders. To induce an overall topological charge, the particles are either confined to a two-dimensional circular cavity with homeotropic boundary or to the surface of a three-dimensional sphere. Both systems exhibit half-integer topological point defects. The isotropic defect core has a radius of the order of one particle length and is surrounded by free-standing density oscillations. The effective interaction between two defects is investigated. All results should be experimentally observable in thin sheets of colloidal liquid crystals.Comment: 13 pages, 16 figures, Phys. Rev.

Two-dimensional nematics in bulk and confined geometries

El pdf del artículo es la versión pre-print: arXiv:1207.3256Two-dimensional nematics possess peculiar properties that have been studied recently using computer simulation and various theoretical models. Here we review our own contribution to the field using density-functional theory, and present some preliminary simulation results on confined two-dimensional nematics. First we discuss the possible stable bulk phases and phase diagrams and the relation between phases and particle geometry. We then explore the adsorption properties on a single substrate and the confinement effects that arise when the fluid is confined between parallel walls. Next, confinement in circular cavities is presented; this geometry allows us to measure some properties of the simplest defects that arise in two-dimensional nematics. Finally, preliminary Monte Carlo simulation results of confined nematics in circular geometry are shown. © 2012 Elsevier B.V.We acknowledge financial support from Comunidad Autónoma de Madrid under the R& D Program of Activities MODELICO-CM/S2009ESP-1691, and from MINECO (Spain) under grants MOSAICO, FIS2010-22047-C01, FIS2010-22047-C04 and FIS2010-22047-C05.Peer Reviewe