Properties of adsorbed oxygen forms on a defective ag(111) surface. DFT analysisстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:A cluster model of an Ag12-3O (ASV) adsorption center using layered silver oxide as a prototype is proposed. The model includes a cation vacancy V on the Ag(111) surface and oxide type subsurface oxygen atoms Oox. Density functional theory (DFT) (B3LYP/LANL1MB approximation) is used to analyze the electronic structure of ASV and oxygen adsorption on this center, ASV+O → AS-O. As shown by the calculations, the adsorbed oxygen is associated with the subsurface oxygen atoms Oss to form structures similar to metal ozonides Ag-Oss-Oep-Oss-Ag-Oox-Ag, containing electrophilic oxygen Oep along with the oxide oxygen Oox. The optical spectra of the ASV and AS-O centers were calculated by the configuration interaction method with single excitations (CIS). For ASV, the most intense absorption bands were obtained in the region 500-700 nm. Oxygen association is accompanied by a sharp decrease in spectrum intensity in the range 600-700 nm and an increase in the intensity of the peak at 500 nm. Vibration frequencies and (IR) intensities were determined for the ASV and AS-O centers. The ASV center exhibits a characteristic spectrum in the region 350-500 cm-1, which corresponds to the frequency spectrum of the surface oxide Ag2O. For associated oxygen forms (AS-O center), the calculations predict additional peaks around 980, 640 and 230 cm-1. These peaks are due to the vibrations of the Oss-Oep-Oss structural unit, stabilized at the cation vacancy.