PAIR DYNAMICS IN HARD-SPHERE FLUIDS - RECOLLISIONAL TIME CORRELATION-FUNCTIONS

Molecular dynamics calculations are reported on dense hard sphere fluids at three packing fractions (η = 0.30,0.40,0.48). Attention is directed to the analysis of correlated recollisions of pairs of particles. The short time dynamics [t≃0(τc) where τc = 1/collision frequency] is governed by correlated backscattering collisions as evidenced by persistence of vector time correlations. For longer times a crossover takes place from the correlated backscattering regime (or geminate recombination) to the diffusive-like regime (nongeminate recombination) in which vector correlations decay faster than scalar correlations. Recollisional events are categorized as first recollisions, second recollisions, and all recollisions. The resulting correlation functions exhibit different evolutionary time scales. Contributions to the time correlation functions (tcfs) from collision sequences involving three and four particles are also separated and analyzed. © 1990 American Institute of Physics.