Theoretical study on defects associated with lead vacancies in PbWO₂ crystals

The defects associated with lead vacancies (V_\rm Pb) in lead tungstate crystals (PbWO_4) are investigated by the relativistic self-consistent discrete variational embedded cluster method. We focus on the density of states and the effect of V_\rm Pb on surroundings. The results show that the existence of V_\rm Pb can diminish the bandwidth of WO_4^ 2- group, however, it can neither produce O^- and Pb^3+ ions nor result in absorptions at 350 and 420 nm. The charge balance of V_\rm P\!b may be evenly compensated by the surrounding oxygen ions.