Self-diffusion and heat flow in isotropic and liquid crystal phases of the Gay–Berne fluid

Abstract

We use the so-called Evans heat flow algorithm and the color conductivity algorithm to calculate the thermal conductivity, λ, and self-diffusion, D, tensors of a model liquid crystal forming fluid, the Gay–Berne fluid. We compared the conductivities of the isotropic phase, the nematic liquid crystal phase, and the smectic B phase and found that the transverse components of λ and D in the nematic phase are about the same as λ and D for the isotropic phase at the same temperature and slightly lower density. The parallel components of λ and D are about two and four times as large as the respective transverse components. In the smectic B phase the parallel thermal conductivity ratio increases to about three, whereas the diffusion coefficient is virtually zero because of the solid like nature of this phase. We cross checked the results by deriving and evaluating the Green–Kubo relations for λ and D using conventional equilibrium molecular dynamics. We also discovered that in the presence of a temperature gradient, the director of the nematic phase, spontaneously aligns itself into the plane perpendicular to the temperature gradient. This effect which is nonlinear in the temperature gradient, minimizes the entropy production in the heat conducting steady state.