Bond-orientational order in liquid Si

We study bond-orientational order in liquid Si via Monte Carlo simulation in conjunction with empirical two- and three-body potentials of the form proposed by Stillinger and Weber. Bond-orientational order (BOO) is described in terms of combinations of spherical harmonic functions. Liquid Si is found to have pronounced short-range BOO corresponding to l=3, as expected for a structure with local tetrahedral order. No long-range BOO is found either in the equilibrium or the supercooled liquid. When the three-body potential is artificially removed, the tetrahedral bond-orientation order disappears and the liquid assumes a close-packed structure.