MODE-COUPLING ANALYSIS OF ATOMIC DYNAMICS IN LIQUID LEAD

A detailed mode-coupling analysis of the atomic self-motion in liquid lead at 623 K is presented and discussed. Time-correlation functions calculated in a large-scale molecular-dynamics simulation were used to derive the relevant memory functions, which were compared with those calculated within the framework of mode-coupling theory. The mode-coupling formalism for the memory function of the velocity autocorrelation function has been extended to wave-vector-dependent memory functions. The detailed analysis of the two sets of memory functions in terms of constituent coupling modes leads to the conclusion that some assumptions incorporated in the present formulation of mode-coupling theory are of limited validity. In particular, the phenomenological form for the memory function proposed by Levesque and Verlet [Phys. Rev. A 14, 408 (1970)] for the Lennard-Jones liquid is found to be inadequate in the case of liquid lead.