This book is about the theory of liquid metals. The interplay between electronic and ionic structure is a major feature of such systems. This should occasion no suprise, as even a pure liquid metal is a two-component system: positive ions and conduction electrons. Therefore, as in a binary liquid mixture such as argon and krypton, where three partial structure factors SArAr, SKrKr, and SArKr are required to describe the short-range atomic order, so in liquid metal Na, for instance, one needs SNa+Na+, SNa+e, and See for a structural characterization.

For a very fundamental treatment, the preceding description would be the correct starting point to treat liquid metal Na. Indeed, the theory of liquid metals has been developed in this manner. However, it is still true that, for many important purposes, a simpler picture suffices. Thus, in the chapter following this outline, attention will be focused on the ion-ion structure factor, which will simply be written as S(k); k = 4π sin θ/λ with 2θ the angle of scattering of X rays or neutrons and λ the wavelength of the radiation. It will be emphasized that it is indeed S(k) that is measured in suitable neutron-scattering experiments.

Then, in the following chapter, the use of this knowledge of structure will be considered in relation to the thermodynamics of liquid metals. Following this, electron screening of ions will be treated with the theme stressed above, the interplay between electronic and ionic structure, leading to a treatment of effective interionic forces. This theory will then be confronted with an approach based on the so-called inverse problem—namely, that of extracting an effective ion-ion interaction from the measured structure factor S(k).