Abstract
We present and discuss the results of calculations of surface relaxations and rumplings for the (001) and (011) surfaces of and using a hybrid B3PW description of exchange and correlation. On the (001) surfaces, we consider both ( or Pb) and terminations. In the former case, the surface layer is found to relax inward for both materials, while outward relaxations of all atoms in the second layer are found at both kinds of (001) terminations and for both materials. The surface relaxation energies of BaO and terminations on (001) are found to be comparable, as are those of PbO and on (001), although in both cases the relaxation energy is slightly larger for the termination. As for the (011) surfaces, we consider three types of surfaces, terminating on a TiO layer, a Ba or Pb layer, or an O layer. Here, the relaxation energies are much larger for the TiO-terminated surface than for the Ba- or Pb-terminated surfaces. The relaxed surface energy for the O-terminated surface is about the same as the corresponding average of the TiO- and Pb-terminated surfaces on , but much less than the average of the TiO- and Ba-terminated surfaces on . We predict a considerable increase of the Ti-O chemical bond covalency near the and (011) surfaces as compared to both the bulk and the (001) surface.
- Received 3 October 2007
DOI:https://doi.org/10.1103/PhysRevB.76.155439
©2007 American Physical Society