Density functional theory applied to the isotropic–nematic transition in model liquid crystals

The isotropic–nematic phase transition is investigated for several model liquid crystals using the density functional method. The models considered are hard ellipsoids of revolution (both prolate and oblate cases), hard spherocylinders, and two additional fluids characterized by pair potentials of a generalized Maier–Saupe type. The direct pair correlation functions for the isotropic phase are obtained by numerical solution of the hypernetted-chain (HNC) and Percus–Yevick (PY) integral equation theories. It is shown that second order density functional theory is strongly dependent upon the approximation used for the isotropic direct pair correlation function. In all cases the density functional results are qualitatively consistent with conclusions based upon orientational stability criteria.