First-principles study on optical spectra of lead vacancies in PbMoO₄

A photochromic effect caused by lead vacancies presents in the yellowish lead molybdate crystals, which seriously affects the application of the crystals in optical instruments. So it is essential to understand the properties caused by intrinsic defects in lead molybdate crystals. In this work, the defect formation energy has been obtained by taking the finite-size (FNV) correction into consideration. The optical spectra also have been gotten under the consideration of electron-phonon coupling. The calculated results indicate that the spectra of the color centers (V-F and V-F(-)) in lead molybdate peaks of 2.43eV and 2.40 eV, respectively, which are in very good agreement with the experimental value of 2.14 eV (580 nm). The positions of the emission peak corresponding to the V-F and V-F(-) color centers are 1.97eV and 1.70eV are consistent with the experimental results (1.8eV and 2.1eV). The absorption band 580 nm coincides with the absorption band obtained from our calculation of the lead vacancy, so we predict that the 580 nm absorption band comes from the lead vacancy.