First-Principles Study on the Electronic Structures for Y³⁺:PbWO₄ Crystals

The possible defect models of Y³⁺:PbWO₄ crystals are discussed by defect chemistry and the most possible substituting positions of the impurity Y³⁺ ions are studied by using the general utility lattice program (GULP). The calculated results indicate that in the lightly doped Y³⁺:PWO crystal, the main compensating mechanism is 2Y_Pb⁺+V_Pb^2-, and in the heavily doped Y³⁺:PWO crystal, it will bring interstitial oxygen ions to compensate the positive electricity caused by Y_Pb⁺, forming defect clusters of 2Y_Pb⁺+O_i^2- in the crystal. The electronic structures of Y³⁺:PWO with different defect models are calculated using the DV-X method. It can be concluded from the electronic structures that, for lightly doped cases, the energy gap of the crystal would be broadened and the 420 nm absorption band will be restricted; for heavily doped cases, because of the existence of interstitial oxygen ions, it can bring a new absorption band and reduce the radiation hardness of the crystal.