Decay of the Velocity Autocorrelation Function
Abstract
Moleculardynamic studies of the behavior of the diffusion coefficient after a long time s have shown that the velocity autocorrelation function decays as s^{1} for hard disks and as s^{32} for hard spheres, at least at intermediate fluid densities. A hydrodynamic similarity solution of the decay in velocity of an initially moving volume element in an otherwise stationary compressible viscous fluid agrees with a decay of (ηs)^{d2}, where η is the viscosity and d is the dimensionality of the system. The slow decay, which would lead to a divergent diffusion coefficient in two dimensions, is caused by a vortex flow pattern which has been quantitatively compared for the hydrodynamic and moleculardynamic calculations.
 Publication:

Physical Review A
 Pub Date:
 January 1970
 DOI:
 10.1103/PhysRevA.1.18
 Bibcode:
 1970PhRvA...1...18A