First-Principles Studies on Electronic Structures and Absorption Spectra of PbWO4 Crystals with Defect VPb^2---VO²⁺ --VPb^2-2-

Electronic structures and absorption spectra for perfect PbWO4 (PWO) crystals and the crystal containing aggregated defectVPb^2---VO²⁺--VPb^2-2-
have been calculated using density functional theory code CASTEP with the lattice structure optimized. The calculated absorption spectra of the PWO crystal containing the aggregated defect VPb^2---VO²⁺--VPb^2-2- exhibit two absorption bands peaking at 1.90eV (650nm) and 3.02eV(410nm). It is predicted that the 420 and 680nm absorption bands are related to the existence of the aggregated defect VPb^2---VO²⁺--VPb^2-2- in the PWO
crystal.