Defect structures in silver chloride

We report a study of the atomic and electronic structure, along with spin densities and energetics, of the primary intrinsic defects in silver chloride in their neutral and charged forms. We have correctly predicted the dominance of the cation Frenkel defect. In agreement with recent studies we have found that both the neutral and charged silver interstitial defects adopt a split-interstitial geometry, with the conventional body-centred interstitial found to be a transition state. We propose that the split-interstitial structure forms four-membered chains which can migrate through the crystal by a knock-on mechanism. We have also studied the structures of the cation and anion vacancies, and seen little relaxation, except on formation of an F-centre, where there is an unusually strong contraction of the nearest-neighbour cations towards the vacant site, which has been proposed to be an ion-size effect.