title: Phase ordering of zig-zag and bow-shaped hard needles in two dimensions.
abstract: We perform extensive Monte Carlo simulations of a two-dimensional bent hard-needle model in both its chiral zig-zag and its achiral bow-shape configurations and present their phase diagrams. We find evidence for a variety of stable phases: isotropic, quasi-nematic, smectic-C, anti-ferromorphic smectic-A, and modulated-nematic. This last phase consists of layers formed by supramolecular arches. They create a modulation of the molecular polarity whose period is sensitively controlled by molecular geometry. We identify transition densities using correlation functions together with appropriately defined order parameters and compare them with predictions from Onsager theory. The contribution of the molecular excluded area to deviations from Onsager theory and simple liquid crystal phase morphology is discussed. We demonstrate the isotropic-quasi-nematic transition to be consistent with a Kosterlitz-Thouless disclination unbinding scenario.
authors.affiliation: Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Tavarone
authors.affiliation: Departments of Chemistry and Physics, Duke University, Durham, North Carolina 27708, USA.
authors.forename: Patrick
authors.initials: P
authors.lastname: Charbonneau
authors.affiliation: Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Stark