Lateral interaction of CO and H2 molecules on ZnO surfaces:: an AM1 study

We have studied the effects of lateral interactions for CO and H-2 adsorbed on large (ZnO)(60) cluster models. The calculations were performed with the AM1 semi-empirical method. The geometric parameters of the adsorbed molecules were fully optimized. CO interacts with the zinc cation located at the site having the lowest coordination at the edge sites between the (0001) and (10 (1) over bar 0) surfaces, The binding energy is increased as we increase the number of adsorbed CO molecules on the ZnO surface. For H-2 molecular interaction, the calculated energy gaps and ionization potentials are modified relative to the bare cluster. We have analyzed the optimized geometric parameters, charge transfer as well as the density of states and compared our results with available experimental data such as density of states, vibrational frequencies, adsorption energies and surface charge. (C) 2000 Elsevier Science B.V. All rights reserved.