Single-Particle and Collective Effects in Liquid Metals Near Freezing and in their Hot Solids

A 'jump' model of single-particle motion in a liquid is first used to calculate the frequency spectrum g(ω) of a liquid metal near freezing. In this treatment g(ω) is characterized by shear (η) and bulk viscosities, plus a time τ breaking the coherence of normal mode oscillations within a 'cell' or subvolume. The connection with earlier treatments of the relation between self-diffusion coefficient D and η at the melting temperature T m of liquid metals is pointed out. The self motion, characterized by g(ω), is considered then in relation to the dynamical structure factor S(q ω) of a liquid metal such as Rb. In particular, theories of the dispersion relation ω q of the collective mode in liquid alkali metals and in their hot solids are re-examined, with -k B Tc(q) used as an effective q space form of a pseudo-pair potential, c being the direct correlation function. This leads to a new proposal for the dispersion relation ω q , which in turn is related to the static structure factor S(q). The close relation of the hot-solid results to the density functional treatment of phonons in K by Ferconi and Tosi is established.