Ab Initio Calculations for the BaTiO₃ (001) Surface Structure

The ab initio method within the local density approximation is applied to calculate cubic BaTiO₃ (001) surface relaxation and rumpling for two different terminations (BaO and TiO₂). Our calculations demonstrate that cubic perovskite BaTiO₃ crystals possess surface polarization, accompanied by the presence of the relevant electric field. We analyse their electronic structures (band structure, density of states and the electronic density redistribution withm emphasis on the covalency effects). The results are also compared with that of the previous ab initio calculations. Considerable increases of Ti-O chemical bond covalency nearby the surface have been observed. The band gap reduces especially for the TiO₂ termination.