Adsorptivity of atomic H and coadsorptivity of Mg and O ions on regular and irregular surfaces of MgO : DFT calculations

An attempt has been made to clarify how the adsorptivity of atomic H and co adsorptivity of Mg and O ions depend on MgO surface irregularities (edge, M g corner, O corner and dislocation) and electrostatic potentials using dens ity functional theory calculations. Quantum clusters of moderate sizes were embedded in simulated Coulomb fields that closely approximate the Madelung potentials of the host surfaces. The results confirm the exclusive depende nce of atomic H adsorption on the coordination numbers of irregular surface s; Surface dislocation drastically enhances the adsorptivity of atomic H, b ut restricts its mobility. Coadsorptivity of Mg and O ion dimers plays a cr ucial role among adsorbates and is always greater than the adsorption energ y of a single adsorbate. Stabilization due to Madelung potential increases on going from the flat to edge to corner surfaces and the three-coordinated corners are the most energetically preferred for nucleation of Mg and O io ns. (C) 2001 Elsevier Science B.V. All rights reserved.