A theoretical investigation of the relaxation effects induced on the ZnO(10(1)over-bar0) surface by the chemisorption of H-2 and CO

Density functional theory coupled to the molecular cluster approach is used to investigate the chemisorption of CO on the clean and Cu doped ZnO(10 (1 ) over bar 0) surface. Results pertaining to the dissociative interaction o f H-2 with ZnO(10 (1) over bar 0) are also presented. Theoretical data incl ude evaluation of surface relaxation upon chemisorption, optimized adsorbat e geometries, adsorbate-substrate binding energies and adsorbate vibrationa l frequencies. According to experiment, the ZnO-CO interaction is found rat her weak, while the Cu-CO bonding results definitely stronger. As far as th e dissociative chemisorption of H-2 on ZnO(10 (1) over bar 0) is concerned, we find that the formation of strong Zn-H and O-H bonds implies the Zn-O b ond breaking. Both vibrational parameters and adsorption energies reasonabl y agree with available experimental measurements. (C) 1999 Elsevier Science B,V. All rights reserved.