First-principles study on the La3+ doping PbWO4 crystal for different doping concentrations

The defect models of La3+: PbWO4 (PWO) for different doping concentrations are discussed by defect chemistry and the optimal substituting positions of the impurity La3+ ions are obtained using the General Utility Lattice Program (GULP). The calculated results indicate that, in the lightly doped La3+: PWO crystal, the main compensating mechanism is [2La+Pb + V2−Pb], and in the heavily doped La3+: PWO crystal, it will bring interstitial oxygen ions to compensate the positive electricity caused by La+Pb, forming defect cluster [2La+Pb + O2−i] in the crystal. The electronic structures of the La3+: PWO with the optimal defect models are calculated using the DV-Xα method. It can be concluded from the electronic structures that, for lightly doped case, the energy gap of the crystal would be broaden and the 420 nm absorption band will be restricted; for heavily doped case, because of the existence of interstitial oxygen ions, it can bring new absorption bands and reduce the radiation hardness of the crystal.