Diffusive and Collective Motion in Classical Fluids

Abstract

A ``perturbation'' technique previously developed is used to generate a systematic sequence of approximate relations between the coherent and incoherent scattering functions of classical fluids measured by inelastic neutron scattering. This sequence, recently obtained independently by Kim and Nelkin, has as its first member the Vineyard convolution approximation, while the second member is Kerr's generalization of this result. We show that the third member leads to a relationship between diffusion and viscosity coefficients of a form previously obtained by very different theories.