Quasimolecular stable forms of oxygen on silver surface. Theoretical analysis by the density functional theory methodстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:A quantum chemical investigation of possible associative oxygen forms on defective silver surface has been performed with the use of gradient- corrected density functional theory (DFT) in the cluster approximation. A surface defect was simulated by a cation vacancy (V). Cluster models (M1: Ag12 and M2: O3Ag12) of an active adsorption site (AS) with a vacancy were chosen on the basis of the structure of high-temperature layered silver oxide. The adsorbed layer on the defective surface was simulated by three oxygen atoms. For the atomic and associative (molecular) forms, the computations gave two stable structures of the adsorbed layer with C3(v) and C2(v) symmetry. The quasimolecular C2(v) structure -Ag-O-O(ep)-O-Ag- resembling metal ozonides is by 44 kcal/mol more stable than the atomic C3(v) structure. The C2(v) structure is singlet and has an electrophilic epoxidizing oxygen atom O(ep). A theoretical estimation of the density of states (DOS) in the quasimolecular oxygen form revealed a complex structure below the 4d band. Additional DOS peaks in this region are due to associative O-O bonds. (C) 2000 Elsevier Science B.V.