Electronic structure of vanadyl pyrophosphate: cluster model studies

The electronic properties of (VO)(2)P2O7(1 0 0) surface are discussed using the cluster model and DFT method. The calculations indicate that present cluster models are size converged and the cluster as large as V10P6O50H30 can be considered the realistic model of the extended (VO)(2)P2O7(1 0 0) surface. Vanadyl pyrophosphate forms a material of a mixed ionic-covalent character. Major covalent contributions participate in the V-O as well as in the P-O binding. The calculations reveal clear electronic differences between structurally different surface oxygen atoms. Triply coordinated oxygen sites (O3) are found to be the most negatively charged. Doubly coordinated oxygen sites (O2) and oxygen atoms singly coordinated to phosphorous are characterize by a similar local reactivity with respect to electrophilic attacks. The strong nucleophilicity of surface oxygen sites together with the V3d character of HOMO/LUMO suggest that the interaction of adsorbate with the (VO)(2)P2O7(1 0 0) surface will lead to the activation of organic species proceeding via to C-H bond splitting. (C) 2001 Elsevier Science B.V. All rights reserved.