First-principle studies of the electronic structure and reflectivity of LaTiO ₃ and Sr doped LaTiO ₃ (La _1-xSr _xTiO ₃)

The electronic structures and optical properties of pure and Sr doped LaTiO ₃ were studied using the first-principle density functional theory (DFT). The results show that the Fermi surface of LaTiO ₃ lies in its conduction band, which makes its reflectivity (about 68.3% at the laser wavelength of 10.6 μm) much higher than other ceramic materials. Sr doping lowers the conduction band and reduces the band gap of La _1-xSr _xTiO ₃ which is beneficial to the prompt of reflectivity. We also found that shifting of the conduction band is not linear with Sr dopant concentration, and a minimum energy level is reached when x∈=∈0.25. For the reflectivity of La _1-xSr _xTiO ₃, it first increases and then decreases with increasing Sr concentration; a maximum reflectivity (99.2%) is achieved when x∈=∈0.25.