Accurate calculation of isotropic-plastic and isotropic-nematic transitions in the hard-ellipsoid fluid

Isotropic and nematic phases of the hard spheroid fluid: a virial approach

We use a high level virial expansion to investigate the properties of the isotropic and nematic phases of the hard spheroid fluid. We use the Monte Carlo techniques described previously to calculate the virial coefficients up to seventh order and we represent the dependence of these coefficients on particle orientations via a spherical harmonic expansion. The expansion coefficients are determined using Lebedev quadrature which carries out the angular integration required exactly. For fairly spherical spheroids (1/3<a/b<3, where a and b are the semiaxes of the spheroid) the virial expansion appears to be convergent in both the isotropic and nematic phases up to high density. For more aspherical particles, the predictions varied in a more erratic fashion upon increasing the number of virials. The use of a finite angular basis set to represent the orientationally dependent virial coefficients could be a contributory cause to this.

Effect of direct correlation functions on elastic constants of molecular liquids

We study the effect of molecule sizes and intermolecular interactions on Frank elastic constants in nematic liquid crystals with ellipsoid of revolution molecules. We use the Poniewierski-Stecki equations which depend on direct correlation functions of ellipsoid molecules and apply the new direct correlation function using the Marko method and contact distance of ellipsoids. The elastic constants for different molecular elongations, using repulsive interaction of hard ellipsoids of revolution and attractive dispersion interaction are calculated. These elastic constants are deduced from a new direct correlation function. It is shown that they are in good agreement with Singh and singh results and qualitatively corresponds to the experiments. The ratios of calculated elastic constants are in agreement with the available experimental results.

Freezing and orientational order in weakly anisotropic fluids

A simple theoretical method of studying the effect of weak anisotropy on the freezing of classical fluids is discussed. Free energy of the solid phase is separated into contributions due to the formation of the regular lattice and the remaining orientational part. The former is calculated by the density-functional theory, while a mean-field theory of orientational order is developed for the latter. An application to the freezing of hard dumbbell fluids yields results in good agreement with simulations.