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)(+) + V-Pb(2-)], 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)(+) + O-i(2-)] in the crystal. The electronic structures of the La3+: PWO with the optimal defect models are calculated using the DV-X alpha method. It can be concluded from the electronic structures I hat, 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. (C) 2006 Elsevier B.V All rights reserved.