Ab initio calculations of the atomic and electronic structure of BaZrO3 (111) surfaces

The paper presents and discusses the results of calculations of surface relaxations and energetics for the polar (111) surface of BaZrO3 using a hybrid B3LYP description of exchange and correlation. On the (111) surface, both Zr- and BaO3-terminations were analyzed. For both Zr and BaO3-terminated BaZrO3 (111) surface upper layer atoms, with the sole exception of BaO3-terminated surface Ba atoms, relax inwards. The Zr-terminated BaZrO3 (111) surface second layer Ba atoms exhibit the strongest relaxation between all Zr and BaO3-terminated BaZrO3 (111) surface atoms. The calculated surface relaxation energy for Zr-terminated BaZrO3 (111) surface is almost fifteen times larger than the surface relaxation energy for BaO3-terminated BaZrO3 (111) surface. The surface energy for Zr-terminated BaZrO3 (111) surface (7.94 eV/cell) is smaller, than the surface energy for BaO3-terminated (111) surface (9.33 eV/cell). The calculated BaZrO3 optical bulk band gap, 4.79 eV is in an excellent agreement with the experimental value, 5.00 eV. The calculated optical band gap for the Zr- and BaO3-terminated BaZrO3 (111) surfaces becomes smaller with respect to the bulk optical band gap.