Structural origin of enhanced translational diffusion in two-dimensional hard-ellipse fluids.

The static correlations and diffusive dynamics of hard ellipses are investigated in the isotropic and nematic phases by Monte Carlo simulation. In particular, an enhancement of the translational diffusion with respect to the rotational diffusion is observed at an onset concentration φ_{on} within the isotropic phase, which is explained in terms of the formation of unstable nematic-like regions with a mean lifetime that exceeds the characteristic time of diffusion at φ_{on}. The relevance to the onset of spatially heterogeneous dynamics in supercooled glass-forming liquids is discussed.