Lateral interaction of CO and H-2 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 th e AM1 semi-empirical method. The geometric parameters of the adsorbed molec ules were fully optimized. CO interacts with the zinc cation located at the site having the lowest coordination at the edge sites between the (0001) a nd (10 (1) over bar 0) surfaces, The binding energy is increased as we incr ease the number of adsorbed CO molecules on the ZnO surface. For H-2 molecu lar interaction, the calculated energy gaps and ionization potentials are m odified relative to the bare cluster. We have analyzed the optimized geomet ric parameters, charge transfer as well as the density of states and compar ed our results with available experimental data such as density of states, vibrational frequencies, adsorption energies and surface charge. (C) 2000 E lsevier Science B.V. All rights reserved.