title: Defect topologies in a nematic liquid crystal near a patchy colloid.
abstract: Using isothermal-isobaric Monte Carlo simulations we investigate defect topologies due to a spherical colloidal particle immersed in a nematic liquid crystal. Defects arise because of the competition between the preferential orientation at the colloid's surface and the far-field director ̂n(0). Considering a chemically homogeneous colloid as a special case we observe the well-known surface and saturn ring defect topologies for weak and strong perpendicular anchoring, respectively; for homogeneous, strong parallel anchoring we find a boojum defect topology that has been seen experimentally [see P. Poulin and D. A. Weitz, Phys. Rev. E 57, 626 (1998)] but not in computer simulations. We also consider a heterogeneous, patchy colloid where the liquid-crystal molecules anchor either preferentially planar or perpendicular at the surface of the colloid. For a patchy colloid we observe a boojum ring defect topology in agreement with recent experimental studies [see M. Conradi, M. Ravnik, M. Bele, M. Zorko, S. Žumer, and I. Muševič, Soft Matter 5, 3905 (2009)]. We also observe two other novel defect topologies that have not been reported thus far neither experimentally nor theoretically.
authors.affiliation: Stranski-Laboratorium für Physikalische und Theoretische Chemie, Fakultät für Mathematik und Naturwissenschaften, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Melle
authors.forename: Sergej
authors.initials: S
authors.lastname: Schlotthauer
authors.forename: Marco G
authors.initials: MG
authors.lastname: Mazza
authors.forename: Sabine H L
authors.initials: SH
authors.lastname: Klapp
authors.forename: Martin
authors.initials: M
authors.lastname: Schoen
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D050866:Liquid Crystals / Q000737:chemistry*; D008956:Models, Chemical; D009010:Monte Carlo Method; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D003102:Colloids