Barcaro Giovanni, Fortunelli Alessandro
Molecular Modeling Laboratory, Istituto per i Processi Chimico-Fisici (IPCF) del CNR, Via G. Moruzzi 1, Pisa, Italy.
Faraday Discuss. 2008;138:37-47; discussion 119-35, 433-4. doi: 10.1039/b705105k.
Binary M2Ag6, M2Ag7, M1Ag7 and M1Ag8 clusters (M = Cu, Au, Pd) adsorbed on an MgO(100) terrace presenting a double vacancy (DV) neutral defect are investigated through a combination of density-functional (DF) biased searches and global optimizations. Alloying allows one to probe the adsorption characteristics of the DV-defected surface. It is found that Au1Ag7 and Au2Ag6 are core-shell magic clusters, in analogy with the pure silver case. The magic character is reduced for Cu1Ag7 and Cu2Ag6, because the shortening of Cu-Ag distances is counteracted by a double-frustration effect due to the DV, and is practically absent for Pd1Ag7 and Pd2Ag6, because the requirements of the metallic bond conduction electron count are in conflict with the metal-surface interaction. However, fluxionality is enhanced for Pd-Ag clusters with respect to the pure silver case, which could influence their catalytic properties.
通过密度泛函（DF）偏向搜索和全局优化相结合的方法，研究了吸附在具有双空位（DV）中性缺陷的MgO(100)台面上的二元M2Ag6、M2Ag7、M1Ag7和M1Ag8团簇（M = Cu、Au、Pd）。合金化使得人们能够探究DV缺陷表面的吸附特性。结果发现，与纯银情况类似，Au1Ag7和Au2Ag6是核壳魔法团簇。对于Cu1Ag7和Cu2Ag6，魔法特性减弱，因为Cu - Ag距离的缩短被DV引起的双挫折效应抵消，而对于Pd1Ag7和Pd2Ag6，魔法特性实际上不存在，因为金属键传导电子数的要求与金属 - 表面相互作用相冲突。然而，相对于纯银情况，Pd - Ag团簇的流动性增强，这可能会影响它们的催化性能。
