Among the various categories of materials, optical materials and the devices based on them play an important role which is increasing every year with the advent of modern photonic technologies and their implementation in everyday life. These materials can be used for converters of electromagnetic radiation, for the design and production of light-emitting diodes operating in the ultraviolet, for more sensitive detectors of ultraviolet radiation and other ionizing radiations as well as for various chemical sensors. This book will give the reader an idea about the utilization of the Density Functional Theory (DFT) for solving complex systems. With the aid of Density Functional Theory (DFT), the many-electron problem can be reduced to a problem with one electron moving in an effective crystal potential.
