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