THEORY OF ELECTRONIC DEFECTS - APPLICATIONS TO MGO AND ALKALI-HALIDES

The topic of electronic defects is introduced with the example of a defect electronic transition, and its role in the F-center lasers. Predictive and methodological objectives of a theory of electronic defects are briefly examined, and general features of a theoretical model of point defects are introduced. The specific theoretical and computational elements of a method bearing the acronym ICECAP are described. They consist of: (i) a quantum molecular defect cluster described in unrestricted Hartree-Fock self-consistent field approximation with Rayleigh-Schrödinger many-body perturbation theory correlation correction; (ii) a classical embedding crystal lattice represented by the shell model; (iii) a treatment of the cluster-lattice boundary condition derived from the Hartree-Fock description of the entire crystal, and including the Kunz-Klein localizing potential; (iv) the static lattice approximation; (v) atomic core pseudopotentials as an option; and (vi) the user-friendly program ICECAP that incorporates the preceding elements in a consistent variational treatment of the total defect lattice. Applications of the method to a number of systems are introduced with a description of several theoretical features that will arise, namely electronic localization and charge transfer, and basis-set and ion-size effects. Details are then given of analyses of the ground states of F centers and hydrogen in MgO and of the Vk center in LiF, the optical properties of Cu+ in NaF and of the F+ center in MgO, and the derivation and application of inter-ionic potentials for impurities and for perfect lattices. Finally, some comments are given regarding short-term and long-term application and development of the method. © 1990.