Ab initio study of point defects in CdF2

The plane-wave pseudopotential method is used to study point defects in CdF2. We present comprehensive results for the native defects as well as for dominant impurities. In addition to F-i, V-Cd and O-F were found to be easily formed compensating acceptors. For In and Ga impurities the experimentally observed large Stokes shift could not be established, and the results rule out symmetric atomic relaxation as the mechanism leading to the bistable behavior. The limitations of the present approach utilizing density-functional theory and the local-density approximation in the case of ionic materials are addressed.