Ab initio calculations of BaTiO3 (111) surfaces

The article presents the results of calculations of polar (111) surface relaxations and energetics using the ab initio code CRYSTAL and a hybrid description of exchange and correlation. Using a hybrid B3LYP approach, the surface relaxation has been calculated for the two possible Ti and BaO3 BaTiO3 (111) surface terminations. For both Ti- and BaO3-terminated BaTiO3 (111) surfaces, the upper layer atoms relax inward. The second layer atoms, with the sole exception of Ti-terminated BaTiO3 (111) surface Ba atom, relax outward. The calculated surface relaxation energy for Ti-terminated BaTiO3 (111) surface is more than two times larger than the surface relaxation energy for BaO3-terminated BaTiO3 (111) surface. The surface energy for Ti-terminated BaTiO3 (111) surface (7.28eV/cell) is smaller, than the surface energy for BaO3-terminated (111) surface (8.40eV/cell).