Density functional cluster studies on the (010) surface of vanadium pentoxide

Ab initio density functional calculations on different surface clusters up to V16O49H18 are used to examine the electronic structure near different oxygen sites at the V2O5(010) surface. Cluster size convergence of the electronic properties is found to be achieved for V10O31H12 or larger clusters. The ionic character of the substrate is confirmed by the atom populations while bond order results show additional covalent binding in agreement with chemical intuition. Terminal (vanadyl) surface oxygens become least ionic, O-0.3 from populations, and bind with one vanadium neighbor by double bonds. One type of bridging surface oxygens becomes O-0.6 and binds with two vanadium neighbors by single bonds, while the other type becomes most negative, O-0.7, and forms four-center bonds involving three vanadium neighbors. The calculated oxygen charge at the V2O5(010) surface suggests an increased local reactivity of the bridging oxygens with respect to electrophilic attacks by adsorbate molecules. This is supported by results From electrostatic potentials calculated from the cluster charge distributions. (C) 1997 Elsevier Science B.V.