SELF-DIFFUSION IN SIMPLE LIQUIDS

Using the combined results of extensive MD simulation and neutron scat tering studies of liquid lead at 623 and 1170 K, details of the self-d iffusion process within the atomic domain are studied. From analysis o f F(s)(q, t) it is found that there is an element of structural relaxa tion in the self-diffusion process which may lead to a jump diffusion component. Also from the derivation of memory functions GAMMA(s)(Q, t) , particularly for the velocity autocorrelation GAMMA(s)(t), it is fou nd that the MD results are not well described by present mode-coupling theories. It is believed that a more sophisticated theory which does not separate the characteristic parts of GAMMA(s)(t) and takes many-bo dy effects into account more properly is needed to explain the observa tions.