Single Particle Motion in Liquid Sodium

Recent neutron scattering experiments on single particle motion in simple liquids and theoretical work together with earlier molecular dynamic simulations have revealed new and interesting insight into the dynamics of a simple liquid. As the experimental results for liquid sodium at several temperatures show, single particle motion can be understood in terms of hydrodynamics in a fairly large range of energy and momentum transfer. Hydrodynamic behavior is shown to extend up to (formula omitted) in the incoherent scattering law S_s(Q, w) and is verified in a low frequency cusp in the density of states z(uj), which corresponds to the long time tail in the velocity-autocorrelation-function (VAF), predicted by molecular dynamic simulations (MD) and mode coupling theories.