Several lattice structures around a Pb vacancy, VPb2−, were optimized by using a plane-wave pseudo-potential formulation within the framework of density functional theory, with a generalized gradient correction. The electronic structures around VPb2− in the PbWO4 crystal were studied by using the molecular cluster model, within the framework of the fully relativistic self-consistent Dirac-Slater theory, by using a numerically discrete variational method. By analyzing the lattice relaxation and electronic structures around VPb2−, it was deduced that, once VPb2− was formed in the PbWO4 crystal, O2− compensated the electrical negativity of VPb2−. That is, Pb2+ could never be the hole-trap compensating VPb2−, and Pb3+ and Pb4+ might not exist in PbWO4 crystals. A possible defect micro-model for VPb2− in as-grown PbWO4 crystals was that each VPb2− created a VK+−VF− aggregate color center.

The Hole Trappers Related to Lead Vacancy in a PbWO4 Crystal. T.Liu, Q.Zhang, S.Zhuang: Solid State Communications, 2004, 132[3-4], 169-73