ABSTRACT
This chapter discusses several examples of application of the semiempirical and first-principles methods to the analysis of the optical and electronic properties of the doped optical materials. The theoretical estimations of the location of the energy levels of the impurity ions in the host’s band gap are yet very difficult. The reason is that the first-principles calculations of the electronic and optical properties of the doped compounds with realistic concentrations of impurity ions imply a use of large supercells and, as consequence, advanced computational facilities. The inorganic solids that are used for optical applications are the dielectrics or semiconductors doped with the transition metal or rare earth ions. Pure or neat hosts, with ideal crystal structure and without any impurities, are characterized by the so-called band gaps, which show the energy difference between the empty conduction band and occupied valence band.
