Bands versus bonds in sulfides: Theoretical investigation of the luminescence of copper in zinc sulfide

The fundamental question of bands versus bonds has been probed through a direct comparison of results from scattered-wave cluster molecular-orbital and augmented-spherical-wave band-structure calculations for copper-activated zinc sulfide phosphor. These methods have been employed to develop a coherent understanding of the process of luminescence for various copper-luminescent centers. Our results for ${\mathrm{Cu}}^{2+}$/ZnS support the Lambe-Klick model for excitation of infrared emission while calculations for ${\mathrm{Cu}}^{+}$,${\mathrm{Cl}}^{\mathrm{-}}$/ZnS and ${\mathrm{Cu}}^{+}$,${\mathrm{Al}}^{3+}$/ZnS support the Schoen-Riehl-Klasens model for green emission. The present study indicates a close correspondence between the two types of calculations and illustrates the utility of using these techniques in a complementary manner to understand the electronic processes in solids.