Abstract
The dissociation of water molecule at the defect free (0 0 1), (1 10) and (2 1 0) five-layer films of the title oxides has been investigated using the periodic HF and DFT levels of ab initio theory together with the 1 x 1 supercell. model in which two water molecules were added to each supercell; one at each side of the film. The water/oxide reaction energies calculated at the HF-level exhibit endothermic character at the (0 0 1) film and exothermic character at the (1 1 0) and (2 1 0) films, while those calculated at the DFT-level always exhibit exothermic character except for the (0 0 1) film of MgO. The interaction energies increase monotonically in the order (0 0 1) < (2 1 0) < (1 1 0) at the HF and DFT levels. The surface morphology of the title oxides is confirmed by considering the binding energies, surface formation energies, relaxation energies, Mulliken population analysis, charge electron density maps, electrostatic potential maps and the vibrational frequencies of the two involved OH bonds at the HF-level. The results were compared with the available experimental data. (C) 2003 Elsevier B.V. All rights reserved.