Energy competition of self-trapped excitons in alkali halides

Abstract

We report the results of the calculation on the stability of self-trapped excitons localized on lattice sites with different geometrical structures in twelve alkali halides; AH, A = Li, Na, K, Rb, and H = Cl, Br, I. Present model leads us to the conclusions that excitons and holes in lithium halides, NaBr and NaI are most stable in energy when they are self-trapped as the three-center type and that those in potassium halides, KCl and NaCl are most stable when they are self-trapped as the two-center type. The energies of the two types of excitons are almost same in KBr and KI. This result shows us an important possibility that the Ex emission comes from the recombination of the three-center type self-trapped exciton.