A Landau-de Gennes theory for hard colloidal rods: defects and tactoids
  We construct a phenomenological Landau-de Gennes theory for hard colloidal rods by performing an order parameter expansion of the chemical-potential dependent grand potential. By fitting the coefficients to known results of Onsager theory, we are not only able to describe the isotropic-nematic phase transition as function of density, including the well-known density jump, but also the isotropic-nematic planar interface. The resulting theory is applied in calculations of the isotropic core size in a radial hedgehog defect, the density dependence of linear defects of hard rods in square confinement, and the formation of a nematic droplet in an isotropic background. 
Jeffrey Everts and Melle Punter and Sela Samin and Paul van der Schoot   and Ren\'e van Roij
cond-mat.soft cond-mat.stat-mech physics.chem-ph