Introduction of density functional theory

In this chapter, the history of quantum theory and the development of density functional theory (DFT) are briefly reviewed. Foundation theorems of DFT, such as Thomas–Fermi model, Hohenberg–Kohn theorem, and Kohn–Sham Equation are introduced in the chapter. The frequently used approximations for the exchange-correlation energy functional are reviewed. In addition, some important concepts of energy band theory, including Bloch's theorem and the first Brillouin zone, are introduced.