A DFT periodic study of the vanadyl pyrophosphate (1 0 0) surface

The unique ability of the vanadyl pyrophosphate (1 0 0) surface to activate n-butane and then selectively oxidize the hydrocarbon to maleic anhydride was studied using modern quantum chem. methods. Bulk (VO)2P2O7, together with stoichiometric and P-enriched (1 0 0) surfaces, were analyzed using periodic d. functional theory calcns. Also simulated was surface ionic relaxation from bulk geometry, and surface hydration. D. of states (DOS) plots show that, whether stoichiometric or P-enriched, bulk terminated or relaxed, bare or hydrated, local covalent reactivity at the (1 0 0) surface is controlled by V species. Terminal P-O oxygen species are the most nucleophilic surface oxygens, as indicated by their predominance of sub-V high-lying valence band levels. A periodic treatment of (VO)2P2O7(1 0 0) hence gives results qual. identical to those obtained from earlier cluster calcns. Simulation of surface ionic relaxation shows that in-plane P-O-V oxygens may also be involved in rupture of substrate C-H bonds for mild oxidn., while surface hydration calcns. indicate that dissociative chemisorption of H2O may play a key role in perpetuation of the selective oxidn. cycle. [on SciFinder (R)]