Density fluctuations in classical monatomic liquids

Abstract

A simple form for the generalized density susceptibility for k approximately 0.5 AA^-1 and omega approximately 10¹³s^-1 is proposed for monatomic liquids which has the merit of satisfying certain sum rules and limits. It is shown to give a good description of the current correlation observed by Rahman (1968) in a molecular dynamics study of argon at 76 K. Moreover at small wavevectors a triple peak structure is obtained with the frequency of the collective excitation in good agreement with a molecular dynamics study of argon by Kurkijarvi, Levesque and Verlet (1968).