ABSTRACT
In this book, we embark on an ambitious journey aimed at understanding and predicting properties of materials from first principles. Such an approach does not involve any adjustable parameter. The only input to the calculation is electronic charge, electron mass, atomic numbers, and masses of the atoms of the material. Materials are made of atoms, which, in turn, are made of electrons and nuclei. Therefore, all the properties of materials can be attributed to the complex behavior of electrons and nuclei interacting with each other. Nuclei are massive compared to electrons and can be handled using classical mechanics except in the case of hydrogen and helium. In solids, the nuclei vibrate about their mean positions. In contrast, electrons do not obey classical mechanics and are governed by quantum mechanics. The behavior of electrons is mainly responsible for all physical and chemical properties of materials. A study of the behavior of electrons in materials and how they are distributed in real space and in different energy levels forms the main subject of electronic structure theory. The electronic structure determines the cohesive energy, which, in turn, determines the structure of the material. The transport, optical, magnetic, and superconducting properties are also governed by the electronic structure. Thus, the electronic structure plays a central role in understanding diverse properties of materials. With the recent advances that have taken place in the electronic structure calculations, now, it is possible to design a new material with desired properties.
