0000000000266516
AUTHOR
William A. Goddard
Theoretical Simulations of Surface Relaxation for Perovskite Titanates
The (100) and (110) surface relaxations are calculated for SrTiO3 and BaTiO3 perovskite thin films Using a semiempirical shell model, the positions of atoms in 16 near-surface layers placed atop a slab of rigid ions are calculated. Surface rumpling and surface-induced dipole moments perpendicular to the surface are calculated for different surface terminations. Surface relaxation is found much larger for the (110) surface. Our results for the (100) surfaces are compared with ab initio calculations and LEED experiments.
Ab initiocalculations of theSrTiO3(110) polar surface
Results of ab initio Hartree-Fock calculations for the SrTiO3 ~110! polar surface are discussed. We have calculated the surface energies, near-surface atomic displacements for four possible terminations ~TiO, Sr, and two kinds of O terminations! as well as Mulliken atomic charges and dipole moments of atoms characterizing their polarization, and the atomic bond populations. We predict a considerable increase of the TiuO chemical bond covalency near the ~110! surface, as compared to both the bulk and the ~100! surface. The O-terminated ~110! surface has surface energy close to that for ~100!, which indicates that both ~110! and ~100! SrTiO3 surfaces can coexist in polycrystals and perovskite…
Atomistic Simulations of the LaMnO3 (110) Polar Surface.
The results of atomic structure calculations, with a focus on the surface relaxation and polarization, are presented for the LaMnO3 (110) O-terminated polar surface. We compare results of the classical shell model calculations for four possible terminations, including (1 × 2) (110) surface reconstruction, and demonstrate that the latter has the lowest surface energy. The surface energy is saturated only when six to eight near-surface atomic planes are relaxed which is accompanied by the considerable dipole moments perpendicular to the surface. Results are compared with those for iso-structural BaTiO3 (110) surfaces.