ABSTRACT
This chapter provides a background for the rest of the book since clearly the electrons within materials are contained within a volume defined by the atomic cores of the material, and it is important to realise that the properties of those electrons are determined largely by their interactions with these atomic cores. In fact, we should go even further and state that the electronic properties of interest in this book are determined exclusively by the energy ‘landscape’ provided by the ionic cores. Therefore, before going further we should look at some of the properties of this ionic background. In the case of crystalline materials this ionic background forms an ionic ‘lattice’, but in other materials, such as amorphous solids, it forms a random aggregate.
