A computer simulation study of liquid crystal phase coexistence.

Results are presented from a variety of molecular simulations of phase coexistence using the well established Gay-Berne (GB) liquid crystal model.Firstly, the simulation of bulk phase coexistence using the Gibbs ensemble Monte Carlo technique is presented, both for one and two-component GB systems. The one-component results, using a novel parameterisation of the GB, show a rich phase behaviour, displaying both isotropic and nematic-vapour coexistence, in good comparison with previous studies. A method for arriving at the two-component parameterisation is then discussed, followed by a novel application of the Gibbs ensemble to the isotropic-nematic transition in two-component systems. Results in broad agreement with theoretical predictions, subject to a large finite size effect, are obtained.Secondly, upon the basis of the one-component Gibbs results, results are presented from a series of molecular dynamics simulations of a free standing GB film in equilibrium with its own saturated vapour. The introduction of inhomogeneity is shown to induce a preferred molecular alignment in the nematic film perpendicular to the liquid-vapour interface. At slightly higher temperatures the nematic film is wet by the isotropic phase, displaying an intermediate ordering regime where the formation of short-lived nematic domains within the film is observed. This effect has been analysed using orientational correlation functions, and shown to result from a decoupling of the planar and perpendicular nematic ordering caused by the system inhomogeneity. A system-size analysis of this effect has also been undertaken, showing a definite increase in the range of decay of these orientational correlations with increasing system size.