Diffusion of univalent impurities in silver halides

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Abstract
The energies which control the diffusion of univalent impurities in AgCI and AgBr have been determined using atomistic simulation methods. These are: the Frenkel defect formation energy, the activation energy for the jump of the impurity ion, and the association energy of the impurity ion with a nearest-neighbour vacancy. Their variation with temperature has been evaluated in the quasi-harmonic approximation. These energies have been used to calculate the diffusion coefficients of Na+ and Cs+ in AgCI and of Na+ and Rb+ in AgBr and the results are compared with experimental data. The effects on the diffusion rate of Na+ in AgCI of changes in the concentrations of both sodium and a divalent impurity (cadmium) have also been determined.