The Structure of Simple Liquid Metals

The theory of the static structure factors of simple
liquid metals is presented,and,in particular,the long-wavelenght
limit of the structure factor is studied by means of the extended
random phase approximation (ERPA) ( Evans and Schirmacher,1978)
and Gaskell's approximation (CA) (Gaskell,1978).
The theoretical structure factors for Rubidium
(T=1900K,350X,313X ), Aluminium (T=13 30K,978K,943K ) and Lead
(T=613K) were computed.lt was found that in all studied cases the
contribution of the terms beyond random phase approximation (RPA)
was smaller than 1%.
It is demonstrated that the Gaskell's approximation can
be obtained by taking the second order MacLaurin expansion of the
inverse structure factor about the reference fluid and neglecting
the reminder term,instead of using the coupling-parameter formula
and expansion of the integrand.This method i3 extended to the
third order MacLaurin expansion.The extra term which is expressed
in terms of the triple density correlation functions is given.
In order to obtain ERPA the theory of classical equilibrium
statistical mechanics of inhomogenous liquids and the generating
functional method are presented.The Weeks-Chandler-
Andersen (WCA, 1971) theory and the 'blip' function method of
Jacobs and Andersen (1975) were utilized to give the structure
factor of the reference fluid.
The characteristic features of the simple liquid metals
are incorporated by means of the effective pair-potential which
represents interactions between pseudo-atoms.The model pseudopotential
of Ashcroft (1968) and the dielectric function of
Vashista and Singwi (1972) have been used to construct this
potential.