Difference in X-ray scattering between metallic and non-metallic liquids due to conduction electrons

The X-ray scattered intensity from a liquid metal as an electron-ion mixture is described using the structure factors, which are exactly expressed in terms of the static and dynamic direct correlation functions. This intensity for a metal is shown to differ from the usual scattered intensity from a non-metal in two points: the atomic form factor and the incoherent (Compton) scattering factor. It is shown that the valence electron form factor, which constitutes the atomic form factor in a liquid metal, leads to a determination of the electron-electron and electron-ion structure factors by combining the ionic structure factor. The authors clarify some confusion which appeared in the proposal by Egelstaff et al. (1974) for extracting the electron-electron correlation function in a metal from X-ray and neutron scattering experiments. A procedure to extract the electron-electron and electron-ion structure factors in a liquid metal is proposed on the basis of the formula for the scattered intensity derived.