Optimal packing of polydisperse hard-sphere fluids

We consider the effect of intermolecular interactions on the optimal size-d istribution of N hard spheres that occupy a fixed total volume. When we min imize the free-energy of this system, within the Percus-Yevick approximatio n, we find that no solution exists beyond a quite low threshold (eta approx imate to 0.260). Monte Carlo simulations reveal that beyond this density, t he size-distribution becomes bimodal. Such distributions cannot be reproduc ed within the Percus-Yevick approximation. We present a theoretical argumen t that supports the occurrence of a nonmonotonic size-distribution and emph asize the importance of finite size effects. (C) 1999 American Institute of Physics.