Molecular simulation and theory of the isotropic-nematic interface

Computer simulations of a simple model of liquid crystals confined between parallel walls have been used to investigate the properties of nematic wetting films and the planar nematic-isotropic interface. Comparison is made with the theoretical predictions of Onsager's density-functional theory, obtained by numerical minimization of the appropriate free energy. Several different anchoring conditions at the wall-nematic interface are investigated. The theory is known to overestimate the bulk coexistence densities, but with this proviso, the agreement between simulation and theory is excellent. For the model studied, simulation and theory give density profiles which vary monotonically through the interface; the simulations also confirm the theoretical prediction that the density profile is shifted towards the nematic phase relative to the order parameter profile. The width of the interface, as measured by the order parameter profile, varies as expected with director tilt angle; the angle-dependence of the density profile width is smaller, and seems to be somewhat overestimated by the theory. (C) 2000 American Institute of Physics. [S0021-9606(00)50412-7].