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 c luster models are size converged and the cluster as large as V10P6O50H30 ca n be considered the realistic model of the extended (VO)(2)P2O7(1 0 0) surf ace. Vanadyl pyrophosphate forms a material of a mixed ionic-covalent chara cter. 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 site s (O3) are found to be the most negatively charged. Doubly coordinated oxyg en sites (O2) and oxygen atoms singly coordinated to phosphorous are charac terize by a similar local reactivity with respect to electrophilic attacks. The strong nucleophilicity of surface oxygen sites together with the V3d c haracter of HOMO/LUMO suggest that the interaction of adsorbate with the (V O)(2)P2O7(1 0 0) surface will lead to the activation of organic species pro ceeding via to C-H bond splitting. (C) 2001 Elsevier Science B.V. All right s reserved.