Our understanding of the electronic structure of matter is based upon theoretical methods of quantum mechanics and statistical mechanics. This chapter reviews fundamental definitions and expressions, including the most basic forms valid for many-body systems of interacting electrons and useful, simplified formulas valid for non-interacting particles. This material is the foundation for succeeding chapters, which deal with further developments of the theory and the methods to carry out calculations.
3.1 Basic equations for interacting electrons and nuclei
The subject of this book is recent progress toward describing properties of matter from theoretical methods firmly rooted in the fundamental equations. Thus ...