Velocity cross-correlations in Lennard Jones and soft sphere fluids: A molecular dynamics simulation study

A deep knowledge of the process of momentum transfer between distinct parti cles is of great interest for understanding the microscopic mechanisms of t he transport properties in liquids. Time correlation functions between the velocity of a tagged particle and velocities of particles within specified ranges of initial separations have been calculated from molecular dynamics simulations of Lennard-Jones and soft-sphere fluids. These functions allow us to build a picture of the spread of the momentum of a central particle o ver the successive shells of neighbours. The influence of both the attracti ve forces in Lennard Jones liquids and the softness of the cores of the int eraction potentials on the characteristics of the momentum transfer process es are discussed. (C) 2000 Elsevier science B.V. All rights reserved.