On the mode-coupling theory for the velocity autocorrelation functions of simple liquids

The velocity autocorrelation functions and the corresponding memory functions for a set of liquid metals and Lennard-Jones fluids have been calculated using it mode-coupling theory. The data required for the theoretical calculations have been obtained from molecular dynamics simulations. The influence of both the short repulsive wall and the attractive well of the potential on the binary and mode-coupling terms of the memory function has been analysed. The mode-coupling theory has been tested by comparing the theoretical results with those directly obtained from computer simulations. The most marked discrepancies correspond to systems showing velocity autocorrelation functions with weak backscattering. In the case of the Lennard-Jones fluids, the binary term of the memory function is less well described using a gaussian function.