First-principles calculations of perovskite thin films

The results of the electronic structure calculations for different surface terminations of SrTiO₃ (100) perovskite thin films are discussed. These calculations are based on ab initio Hartree-Fock method with a posteriori electron correlation corrections and density functional theory with a number of different exchange-correlation functionals, including hybrid (B3PW, B3LYP) exchange techniques. Results are compared with previous ab initio plane-wave local density approximation and classical shell model calculations. Calculated considerable increase of the Ti-O chemical bond covalency nearby the surface is confirmed by experimental data. We predict also the band-gap reduction, especially for TiO₂ termination.