The structure of the interface-stabilized c(4 x 2) Ni3O4/Pd(100) monolayer was determined by using low energy electron diffraction I–V experiments. Tensor low-energy electron diffraction simulations converged to a Rp factor of 0.22 with a structural model based on the NiO(100) surface, where all the atoms of the oxide phase were coplanar. In order to obtain the correct c(4 x 2) periodicity of the phase, a Ni vacancy array was introduced into the model. In details, O atoms sit on top of Pd atoms, while Ni atoms occupy the fourfold hollow sites. The lattice constant of NiO was contracted in order to match the substrate periodicity, and only a very small buckling of the Ni atoms (0.04Å) was introduced. The most relevant change with respect to a rigid NiO(100) structure was the in-plane displacement of O atoms by about 0.2Å along directions almost coinciding with the <010> substrate azimuths, away from the vacant Ni site. The proposed structure was perfectly compatible with the scanning tunnelling microscopic images preliminarily reported in the literature.

A LEED I–V Structural Determination of the c(4 x 2) Ni3O4/Pd(100) Monolayer Phase - an Ordered Array of Ni Vacancies. S.Agnoli, M.Sambi, G.Granozzi, A.Atrei, M.Caffio, G.Rovida: Surface Science, 2005, 576[1-3], 1-8