First-Principles Calculations of the Atomic and Electronic Structure of CaTiO3 (111) Surfaces

The results of calculations of CaTiO3 polar (111) surface relaxations, rumplings, energetics, optical band gaps, and charge distribution using the ab initio code CRYSTAL and a hybrid description of exchange and correlation are presented. Using a hybrid B3LYP approach, the surface relaxation for the two possible Ti and CaO3 CaTiO3 (111) surface terminations are calculated. For both Ti and CaO3-terminated CaTiO3 (111) surfaces upper layer atoms relax inwards, while the second layer atoms, with the sole exception of CaO3-terminated surface Ca atom, relax outwards. Calculated surface relaxation energy for Ti-terminated CaTiO3 (111) surface is more than five times larger than the surface relaxation energy for CaO3-terminated CaTiO3 (111) surface. The surface energy for Ti-terminated CaTiO3 (111) surface (4.18 eV/cell) is smaller, than the surface energy for CaO3-terminated CaTiO3 (111) surface (5.86 eV/cell).