Rajesh Chinagandham, Nigam Sandeep, Majumder Chiranjib
RMC, Bhabha Atomic Research Centre, Mumbai, India-400094.
Phys Chem Chem Phys. 2014 Dec 28;16(48):26561-9. doi: 10.1039/c4cp02137a.
We report the structural and electronic properties of Aun (n = 1-7 and 10) clusters supported on a clean α-Al2O3(0001) surface using the spin-polarized version of the plane wave based pseudo-potential method. To underscore the effect of support interaction, the geometries of the deposited Au clusters are compared with the gas-phase structures. In general, the trend in the growth pattern shows that all deposited Au clusters favor planar configurations, similar to that in the isolated case. However, due to the roughness of the Al2O3(0001) surface the deposited Au atoms are arranged in a zig-zag pattern. The binding energy of an Au atom on the Al2O3 surface is 0.79 eV and it binds to the surface Al atom. Two Au atoms prefer to form a dimer on the alumina surface rather than adsorbing as a monomer at a long distance. As the size of the cluster increases the adsorption energy shows a decreasing trend. The nature of chemical bonding at the interface is established by the charge distribution analysis, which suggests an overall charge transfer from the surface to the Au cluster. The additional negative charge on the deposited Au cluster corroborates the red shift of the energy levels of the Au-Al2O3 composite in comparison to the isolated Aun clusters. Further investigations were carried out by analyzing the interaction between the oxygen molecule and the Aun@Al2O3 system, a prototype to study the oxidation mechanism. The results reveal that the interaction of O2 with Aun@Al2O3 follows a dissociative chemisorption route and ruptures the O-O bond.
我们使用基于平面波赝势方法的自旋极化版本，报道了负载在清洁的α-Al2O3(0001)表面上的Aun（n = 1 - 7和10）团簇的结构和电子性质。为了强调载体相互作用的影响，将沉积的金团簇的几何结构与气相结构进行了比较。一般来说，生长模式的趋势表明，所有沉积的金团簇都倾向于平面构型，这与孤立情况下的情况类似。然而，由于Al2O3(0001)表面的粗糙度，沉积的金原子以锯齿形排列。金原子在Al2O3表面的结合能为0.79 eV，它与表面的铝原子结合。两个金原子更喜欢在氧化铝表面形成二聚体，而不是以单体形式远距离吸附。随着团簇尺寸的增加，吸附能呈下降趋势。通过电荷分布分析确定了界面处化学键的性质，这表明存在从表面到金团簇的整体电荷转移。与孤立的Aun团簇相比，沉积的金团簇上额外的负电荷证实了Au-Al2O3复合材料能级的红移。通过分析氧分子与Aun@Al2O3体系之间的相互作用进行了进一步研究，该体系是研究氧化机理的一个原型。结果表明，O₂与Aun@Al2O3的相互作用遵循解离化学吸附途径并断裂O - O键。
