Inter-ionic potentials and structure factors in liquid alkali metals

Abstract

The inter-ionic potentials phi (r) in the alkali metals and the possibilities of estimating them from data on the structure factors S(k) are discussed. The dependences of phi (r) on the density and on the form of the pseudopotential model used are investigated. The structure factor is calculated in the Percus-Yevick (PY) approximation which has been shown previously to describe the region of the main peak of S(k) very accurately. phi (r) and S(k) are found to be rather sensitive to the choice of the pseudopotential and the approximation for screening. The form of S(k) is determined primarily by the effective packing fraction, i.e. by the ratio of the effective volume of the repulsive core of phi (r) to the atomic volume, and is less sensitive to variations of the attractive part of phi (r). Potentials phi (r) are presented corresponding to the pseudopotential model discussed earlier which gives a very accurate description of all the atomic properties of solid alkali metals. The S(k) calculated with these phi (r) are shown to be in good agreement with the available data for liquid alkali metals over wide ranges of temperatures and densities.