CREATION AND RECOMBINATION OF FRENKEL DEFECTS IN AGBR

Complete ionic conductivity spectra as well as quasielastic and inelas tic neutron scattering spectra have been taken of solid silver bromide at various temperatures. High-amplitude vibrational movements, essent ially of the silver ions, contribute to both kinds of spectra. In part icular, a conductivity maximum, located at about 500 GHz, reflects osc illations of individual silver ions along [111] directions. - The micr owave and millimetre-wave conductivities are dominated by a thermally activated Debye-type relaxation process. The effect is consistently ex plained by the frequent hopping of silver. ions from regular octahedra l lattice sites into tetrahedral interstitial sites and back again, i. e., by the frequent creation and recombination of Frenkel pairs. - The effect is also responsible for the existence of thermally activated q uasielastic components in the neutron scattering spectra. The width of the coherent quasielastic scattering shows that the forward-backward hopping of a silver ion is accompanied by fast correlated movements of ions in its immediate neighbourhood.