Ab initio study of SrTiO3 surfaces

We present first-principles total-energy calculations of (001) surfaces of SrTiO3. Both SrO-terminated and TiO2-terminated surfaces are considered, an d the results are compared with previous calculations for BaTiO3 surfaces. The major differences are in the details of the relaxed surface structures. Our calculations argue against the existence of a large ferroelectric rela xation in the surface layer, as had been previously proposed. We do find so me indications of a weak surface ferroelectric instability, but so weak as to be easily destroyed by thermal fluctuations, except perhaps at quite low temperatures. We also compute surface relaxation energies and surface elec tronic band structures, obtaining results that are generally similar to tho se for BaTiO3. (C) 1998 Elsevier Science B.V. All rights reserved.