Simulation of the defect pair VPb–VO in PbMoO4 crystals

A simulation study has been performed to investigate the defects in PbMoO4, based on the interatomic potentials empirically fitted to the known crystal properties. The formation energies of the isolated point defects VPb2-, VO2+, the cluster defects VPb2-–VO2+, VPb2-–VO2+–VPb2- and VO2+–VPb2-–VO2+ have been calculated. It is theoretically demonstrated that most of VPb2- and VO2+ in the as-grown PbMoO4 crystal exist in the form of the vacancy pair VPb2-–VO2+, which would play important roles in the formation and transformation process of photo-chromic effect in PbMoO4 crystal.