Microscopic theory of dynamics in an orientationally ordered fluid

Abstract

A variety of dynamical properties are studied in a model complex liquid composed of hard parallel spherocylinders. For this fluid a revised Enskog kinetic theory (RET) is introduced. In the long wavelength and long time limit the RET leads to liquid crystal nematic-like hydrodynamic equations with explicit expressions for all transport coefficients in terms of an assumed known equilibrium two-point distribution function. The transport process of self-diffusion in this fluid is also studied in the Enskog approximation. This model has a nematic to smectic phase transition (N→A) where a one-dimensional translational order occurs. Near this phase transition the RET is shown to lead to a van Hove-like theory of critical dynamics. The critical mode near the N→A transition is analogous to the so-called soft extended heat mode recently discussed for simple fluids. Near the N→A transition the critical singularities in the nematic viscosities are discussed. It is shown that the singularities arise from the same mode coupling mechanism that is responsible for the anomalously slow relaxation of the stress-tensor autocorrelation function in dense simple liquids.