Influence of the asymptotic behaviour of G( q) on the structure of simple liquid metals

Abstract

The asymptotic dependence of the local-field correction function, G( q), is investigated in determining the structure of simple liquid metals. We compare two variants of G( q), the well-known one of Ichimaru and Utsumi, and the more recent one proposed by Farid and co-workers. As the wavevector q tends to zero, both functions coincide exactly, while as q tends to infinity the former has a horizontal asymptote and the latter has a parabolic dependence. After computing the pair potential, u( r), for Na and Al with both local-field functions, we deduce the structure factor, S( q), and the pair distribution function, g( r), in the framework of the soft-core mean spherical approximation. It is shown that u( r), g( r), and S( q) are very sensitive to the low- q ( q<2 k F) behaviour of G( q), but quite not to its large- q one.