Role of triplet correlations in anomalous self-diffusion coefficient

Abstract

Self-diffusion coefficient and velocity auto correlation function of fluid interacting via the Gaussian core potential have been studied using Mori–Zwanzig memory function formalism. Two and three body contributions to second and fourth frequency sum rules of velocity auto correlation function have been calculated. These sum rules and an ansatz for the memory function have been used to study the time evolution of velocity auto correlation function for different densities and temperatures. Results obtained are compared with the available molecular dynamics simulation results and are found to be in good agreement. Contribution due to three body correlations is found to play a significant role in anomalous behaviour of self-diffusion coefficient and velocity auto correlation function.