title: Orientational ordering of hard zigzag needles in one dimension.
abstract: The orientational ordering and the tilt angle behavior of a one-dimensional fluid of hard zigzag needles are examined by means of transfer matrix method and Onsager theory. The centers of mass of the particles are restricted to a line, while the orientational unit vectors are allowed to rotate freely in two dimensions. It is shown that zigzag needles do not undergo an isotropic-nematic phase transition, but the system is always in an orientationally ordered phase where the order parameter increases with the density. For hard needles and any other kinds of particles with an axis of symmetry the orientational distribution function is symmetric around its maximum value and the nematic director is perpendicular to the layer. For zigzag needles, which have nonconvex shape without an axis of symmetry, the orientational order is anisotropic around its maximum value and the nematic director is density dependent even at very high densities, i.e., the structure of one-dimensional fluid is always tilted. It is found that the density dependence of the tilted structure depends strongly on the shape of the zigzags. Surprisingly, the Onsager theory produces quite accurate results for the order parameters and tilt angles even in very dense systems.
authors.affiliation: Institute of Physics and Mechatronics, University of Pannonia, P.O. Box 158, Veszprém H-8201, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Gurin
authors.forename: Szabolcs
authors.initials: S
authors.lastname: Varga