Heard Christopher J, Heiles Sven, Vajda Stefan, Johnston Roy L
Department of Applied Physics, Chalmers University of Technology, SE 412-96 Gothenburg, Sweden.
Nanoscale. 2014 Oct 21;6(20):11777-88. doi: 10.1039/c4nr03363a. Epub 2014 Aug 26.
The novel surface mode of the Birmingham Cluster Genetic Algorithm (S-BCGA) is employed for the global optimisation of noble metal tetramers upon an MgO (100) substrate at the GGA-DFT level of theory. The effect of element identity and alloying in surface-bound neutral subnanometre clusters is determined by energetic comparison between all compositions of PdnAg(4-n) and PdnPt(4-n). While the binding strengths to the surface increase in the order Pt > Pd > Ag, the excess energy profiles suggest a preference for mixed clusters for both cases. The binding of CO is also modelled, showing that the adsorption site can be predicted solely by electrophilicity. Comparison to CO binding on a single metal atom shows a reversal of the 5σ-d activation process for clusters, weakening the cluster-surface interaction on CO adsorption. Charge localisation determines homotop, CO binding and surface site preferences. The electronic behaviour, which is intermediate between molecular and metallic particles allows for tunable features in the subnanometre size range.
在广义梯度近似密度泛函理论（GGA-DFT）水平下，采用新型伯明翰聚类遗传算法（S-BCGA）对MgO（100）衬底上的贵金属四聚体进行全局优化。通过比较PdnAg(4-n)和PdnPt(4-n)所有组成的能量，确定了表面结合中性亚纳米团簇中元素特性和合金化的影响。虽然与表面的结合强度按Pt > Pd > Ag的顺序增加，但过剩能量分布表明这两种情况下都倾向于混合团簇。还对CO的吸附进行了建模，结果表明吸附位点仅可通过亲电性来预测。与单个金属原子上CO吸附的比较表明，团簇的5σ-d活化过程发生了反转，削弱了CO吸附时团簇与表面的相互作用。电荷局域化决定了同拓扑性、CO结合和表面位点偏好。电子行为介于分子和金属粒子之间，使得亚纳米尺寸范围内具有可调谐特性。
