Nematic-isotropic phase transition: An extended mean field theory

The small magnitude of (Tc-T*)/Tc, where Tc is the nematic-isotropic phase transition temperature and T* denotes the virtual transition temperature, has been a long-standing puzzle in the physics of liquid crystals. We show that by extending the mean field theory to include the isotropic, density-dependent component of the molecular interaction the magnitudes of both (Tc-T*)/Tc and the density change at the transition automatically become in accord with the experimental values. In addition, the theory yields a value of dTc/dp, where p denotes pressure, that is on the same order as the experiment.