Electronic structures and optical dielectric functions of room temperature phases of SrTiO_3 and BaTiO_3

摘要

We investigate the electronic structures and optical dielectric functions of the room temperature phases of SrTiO_3 and BaTiO_3 by using Tran and Blaha's modified Becke and Johnson exchange potential. Calculated energy gaps are substantially better than previous first-principles results with respect to experimental values, further calculated optical dielectric functions as functions of photon energy are in good agreement with experimental curves, and calculated zero frequency refractive indexes are also consistent with experiment. This substantial improvement is achieved because the energy levels of the Ti d states are correctly calculated with this new exchange potential. These make a reasonable, reliable understanding of the electronic structures and optical properties of room temperature phases of SrTiO_3 andBaTiO_3. This approach should be applicable to other semiconducting materials.