First-principles calculations for SrTiO₃(1 0 0) surface structure

As a continuation of our recent ab initio calculations of SrTiO₃(1 0 0) surface relaxation for the two different terminations (SrO and TiO₂) [Phys. Rev. B 64 (2001) 23417], we analyze here their electronic structures (band structure, density of states, and the electronic density redistribution with emphasis on the covalency effects). We compare results of ab initio Hartree-Fock method with electron correlation corrections and density functional theory with different exchange-correlation functionals, including hybrid (B3PW, B3LYP) exchange techniques. Our results are also compared with previous ab initio plane-wave local density approximation calculations and experiments when available. Considerable increase of Ti-O chemical bond covalency nearby the surface and the gap reduction, especially for the TiO₂ termination, are confirmed.