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 cr ystal introduced by one of us a few years ago. A systematic exploratio n of the phase diagram using density-functional theory has revealed th at, for sufficiently anisotropic interaction potentials, ordinary liqu id-vapour coexistence is preempted by a direct transition between a lo w-density disordered fluid phase and a nematic phase. Furthermore, coe xistence between two nematic phases has been found, for fluids charact erized by soft repulsive isotropic interactions, in addition to the ha rd-core and Maier-Saupe potentials.