MOLECULAR-DYNAMICS SIMULATIONS FOR THE DENSITY AUTOCORRELATION FUNCTION IN A SUPERCOOLED FLUID-PHASE

We have re-calculated the self part of the density autocorrelation fun ction F(s)(k, t) (incoherent scattering function) for the binary soft- sphere fluid with a much longer molecular-dynamics (MD) simulation tha n our previous MD calculations, and with a larger system size (N = 400 0) to a longer time window as well as to study a system-size dependenc e, if it exists. The full density autocorrelation function F(k, t) was also computed. it is found that all F(k, t)'s that we have computed i n this work can be fitted over a wide range of time steps (at least ov er three figures of the decay) by a Williams-Watts stretched exponenti al function F(s)(k, t) = A exp[-(t/t0)beta], where A, beta and t0 are adjustable parameters. Other significant dynamical behaviours were als o presented in mean square displacements and non-Gaussian parameters f or highly supercooled fluids with N = 4000. The present results are co mpatible to our previous computations with N = 500, but a significant size dependence is suggested.