Long-Time Behavior of the Velocity Autocorrelation Function for a Fluid of Soft Repulsive Particles

By a molecular-dynamics simulation of a three-dimensional system of 4000 particles, we show that the long-time tail of the velocity autocorrelation function has the form ${\alpha }_0{t}^{-\frac{3}{2}}$, where $t$ is the time and ${\alpha }_0$ a coefficient depending on the kinematic viscosity and on the diffusion coefficient.