On the electronic structure of the pure and oxygen covered Ru(0 0 0 1) surface

The bonding properties between the Ru atoms of a pure and of an oxygen covered Ru(0 0 0 1) surface are investigated by an analysis of ab initio band-structure data with the concept of the covalent bond energy. The results are consistent with the observed inward relaxation of the topmost Ru layer for the pure surface and the outward relaxation for the oxygen covered surface, and a reinterpretation of the outward relaxation is given.