A model nematic liquid crystal revisited: some new phase diagrams from density-functional theory

We have reconsidered a simple Maier-Saupe model of a nematic liquid crystal introduced by one of us a few years ago. A systematic exploration of the phase diagram using density-functional theory has revealed that, for sufficiently anisotropic interaction potentials, ordinary liquid-vapour coexistence is pre-empted by a direct transition between a low-density disordered fluid phase and a nematic phase. Furthermore, coexistence between two nematic phases has been found, for fluids characterized by soft repulsive isotropic interactions, in addition to the hard-core and Maier-Saupe potentials.