Paper SS1+NC-ThA11
Water-Stabilized Reconstructions on Polar Surfaces of Rocksalt Oxides

Thursday, October 23, 2008, 5:20 pm, Room 207

We have investigated the stabilizing effect of water on the √3x√3-R30^o and 2x2 reconstructions of the MgO(111) and NiO(111) surfaces using a combination of x-ray photoelecton spectroscopy (XPS) and transmission electron diffraction (TED). Combined experimental analysis has confirmed that the MgO(111)-√3x√3-R30^o is stable only in the presence of hydroxyl groups on the surface, which is contrary to previously published structures. Experimental refinements of the valence charge density at these surfaces will also be discussed. Our experimental studies have been coupled with full-potential, all-electron density functional theory calculations to estimate surface energies and perform structural relaxations. The NiO system is particularly difficult to calculate due to highly localized and correlated 3d electrons. This has necessitated the use of a hybrid exchange-correlation functional in which the generalized gradient approximation is augmented with a 25% mixing of Hartree-Fock exact exchange for the 3d shell. This methodology substantially improves the accuracy of DFT-calculated surface energies, sometimes by several eV.