Spatial distribution of the conduction-band particle density in silver halides

In a recent paper [M. T. Bennebroek et al., Phys. Rev. B 54, 11276 (1996)] shallow electron centers in AgBr and AgCl have been investigated by pulsed ENDOR. From an analysis of these data in terms of the effective-mass approx imation it has been concluded that the states at the bottom of the conducti on band, commonly believed to be solely due to silver 5s states, must have a contribution from halogen s states that is too large to be accounted for by a one-electron theory. We have calculated the hyperfine interaction fdr these states using an nb initio calculation based on the local spin-density approximation of the density-functional theory. Our results which are in c lose agreement with the published experimental data show that the halogen s -like contributions to the conduction-band states are much more localized t han the corresponding unoccupied atomic s states. Shallow electron centers in silver halides seem to be the first systems for which the ligand hyperfi ne interactions are quantitatively described within the effective-mass appr oximation.