ON THE MODE-COUPLING THEORY FOR THE VELOCITY AUTOCORRELATION FUNCTIONS OF SIMPLE LIQUIDS

The velocity autocorrelation functions and the corresponding memory fu nctions for a set of liquid metals and Lennard-Jones fluids have been calculated using it mode-coupling theory. The data required for the th eoretical calculations have been obtained from molecular dynamics simu lations. The influence of both the short repulsive wall and the attrac tive well of the potential on the binary and mode-coupling terms of th e memory function has been analysed. The mode-coupling theory has been tested by comparing the theoretical results with those directly obtai ned from computer simulations. The most marked discrepancies correspon d to systems showing velocity autocorrelation functions with weak back scattering. In the case of the Lennard-Jones fluids, the binary term o f the memory function is less well described using a gaussian function .