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| - Chemical Properties of Small Au Clusters: An Analysis of the Local Site Reactivity
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| - The chemical properties of small gold clusters Aun with n up to 10 atoms were investigated using densityfunctional theory (DFT). These clusters have planar structures, and we analyzed the effects of the planarityon the chemistry of the clusters. Using atomic hydrogen as a chemical probe, we found a strong site dependenceof the reactivity: the H atoms preferentially react at regions on the rim of the planar cluster. A strongdirectionality of the bonds formed was also observed. Bonds in directions contained in the plane of the Aucluster are preferred, and bonds along the direction perpendicular to the cluster plane are generally unfavorable.These features are rationalized in terms of the spatial distribution of the frontier orbitals and the Fukui functions.We also found a strong odd−even oscillation of the reactivity with cluster size, which can be explained fromthe occupation of the frontier orbitals. Finally, we explored the influence of the site-dependence reactivityand the directionality of the bonding on the conformations of these small Au clusters when supported onoxide surfaces (MgO and TiO2). Such directionality has the effect of favoring “upright” geometries on perfectoxide substrates. Adsorption on substrates with oxygen vacancies is characterized by a competition betweenupright and quasi-horizontal conformations of the supported cluster.
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