First-principles study on electronic structure and absorption spectra for the CaWO4 crystal with oxygen vacancy

The electronic structure and absorption spectra for the perfect CaWO₄ and the CaWO₄ containing oxygen vacancy have been calculated using density functional theory code CASTEP with the lattice structure being optimized. The results indicate that the CaWO₄ crystal containing , an additional absorption spectrum in the region of visible light. And the absorption spectrum can be fit into two Gaussian-shape absorption spectra with peaks at 360 and 415 nm. These peaks are located at the experimentally observed position. It is predicted that the 340 and the 420 nm absorption spectra are related to the existence of in the CaWO₄ crystal.