Unrestricted-Hartree-Fock cluster analysis ofFandFAcenters in some alkali halides

Abstract

Unrestricted-Hartree-Fock cluster calculations are reported, which include the nearest-neighbor ions of $F$ centers in the lithium and potassium halides, and of $F_A\left(\mathrm{Li}\right)$ centers in the potassium halides. The Coulomb potential of a surrounding lattice of point ions is included. Optical-absorption energies, including $F_A$ splitting, are found to be in satisfactory agreement with experiment, but ground-state hyperfine-structure constants generally are not. Spin-polarization and impurity-ion-displacement effects are also examined.