Molecular Chaos, Pair Correlations, and Shear-Induced Ordering of Hard Spheres

We present results of molecular dynamics simulations that show that the shear-induced ordering of hard spheres is preceded by the apparent decrease to zero (in certain directions) of the anisotropic pair-distribution function (PDF) at contact. This precursor to the ordering is explained on the basis of a careful interpretation of the meaning of “molecular chaos” in hard-sphere systems. An ansatz is proposed to model the nonequilibrium PDF at finite separations and is shown to compare well with simulations.