Dynamical structure factor of dense gases

Abstract

The space-time memory function associated with the dynamical structure factor is expressed in terms of current-current and density-current correlation functions. We then apply the binary-collision expansion to evaluate these correlation functions. In this approximation, we include exactly all the effects of a single collision between a pair of particles. The dynamical structure factor is then evaluated from the memory function and compared with the neutron scattering data on dense krypton gas. The agreement is very good even for wave numbers below the first diffraction peak in the structure factor, indicating that the spatial correlations are included in this theory.