O-Ru(0001) surface bond and band formation

Incorporating the bond-to-band and the potential barrier model [J. Phys. Chem. Solids 58, 903 (1997); J. Phys.: Cond. Matt. 27, 5823 (1997)] into the existing database reveals that the O-Ru(0001) triphase results from the formation of O-1, hybridized O-2 and the addition of a virtual bond, respectively. Oxygen is located at the center of a tetrahedron, forming a Ru4O cluster. Initially (< 1/4 ML), the Ru4O (O-1 + Ru+ + 3Ru dipole) forms, retaining C-3v symmetry. Then (1/2 ML), the Ru4O develops into a Ru2O (O-2 + 2Ru(+) + 2Ru dipoles) by forming another bond with a surface Ru atom; as a result, a dipole-ion pairing row forms. Finally (1.0 ML), a virtual bond [2Ru(dipoles)(+)] forms by redistributing the dipole electrons; this process not only reduces the dipole moment but also narrows the antibond subband. The first layer spacing depends upon bond geometry and the second layer spacing contracts due to charge redistribution.