First-principles studies of the effect of oxygen vacancies on the electronic structure and linear optical response of multiferroic BiFeO3

Oxygen vacancies (OVs) have a significant influence on the carrier mobility and optical conductivity in transition metal oxides. In this letter, using density-functional theory, we investigate the effect of OVs on the optical response in multiferroic BiFeO3. Within the generalized gradient approximation plus the on-site Coulomb repulsion, we show that the absorption edge shifts to lower energy with the increase of OV concentration, while the location of the main absorption peak does not change. The agreement between theoretical calculations and experimental measurements of the dielectric function is greatly improved when OVs are considered. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3272107]