Clean and hydrated low-index RbTiO surfaces.

Despite the remarkable dielectric properties of RbTiO upon exposure to a humid atmosphere, its surfaces are still poorly known, to date. Here we study the atomic-scale structure of the clean (100), (010) and (001) surfaces, and the onset of water adsorption density functional theory. Among them, the clean (001) surface has a very low surface energy, much smaller than most terminations of other perovskites or titania. RbTiO (001) is also very reactive towards water, which adsorbs as a molecule, forming regular water arrays on the surface. From the calculations, we conclude that RbTiO could very easily cleave under ambient conditions, forming (001) planes with ordered adsorbed water and almost null surface stress. Although RbTiO is a three-dimensional crystal, it behaves in this respect as a two-dimensional compound, such as graphite or layered perovskites.