MODELING OF DEFECT PROPERTIES OF SILVER AND ITS IONS IN ALKALI FLUORIDES

Electron paramagnetic resonance studies have shown that the silver ion , Ag+, can act as a trap for both electrons and holes in irradiated al kali halide crystals, forming Ag0 and Ag2+ ions. In this paper we repo rt the results of a simulation study using an embedded cluster approac h, called ICECAP, thereby obtaining the ground state configuration and the charge stability of silver in the alkali fluorides, LiF, NaF, and KF. The icecap code combines the quantum cluster treated by the Hartr ee-Fock approximation and the embedding shell model lattice self-consi stently. The calculations suggest that a Jahn-Teller distortion of the lattice will occur for the case of the Ag2+ ion, thereby causing the local environment of the ion to descend to tetragonal symmetry. The la tter has been confirmed by an electron paramagnetic resonance (epr) st udy for Ag doped in KF.