New Infrared Properties of the Tetragonal CaTiO₃

First-principle calculations are performed to study the infrared optical and electronic properties of the tetragonal CaTiO₃. We find that dielectric function and reflectivity exhibit a new single-peak infrared spectrum. It is shown that strong orbital hybridization can form the dipole distribution of covalent bonds (Ti-O₁ and Ti-O₂) and can result in anomalous optical behaviour. The tetragonal structure that determines the dipole configuration and leads to the optical dipole-dipole transition forbidden is therefore realized to be vital to cause such optical phenomena with the insulator feature.