Bochicchio Davide, Ferrando Riccardo, Novakovic Rada, Panizon Emanuele, Rossi Giulia
Physics Department, University of Genoa and CNR-IMEM, Via Dodecaneso 33, 16146, Genoa, Italy.
Phys Chem Chem Phys. 2014 Dec 28;16(48):26478-84. doi: 10.1039/c4cp02143f.
Chemical ordering in magic-size Ag-Pd nanoalloys is studied by means of global optimization searches within an atomistic potential developed on the basis of density functional theory calculations. Ag-rich, intermediate and Pd-rich compositions are considered for fcc truncated octahedral, icosahedral and decahedral geometric structures. Besides a surface enrichment in Ag, we find a significant subsurface enrichment in Pd, which persists to quite high temperatures as verified by Monte Carlo simulations. This subsurface Pd enrichment is stronger in nanoparticles than in bulk systems and is rationalized in terms of the energetics of the inclusion of a single Pd impurity in an Ag host nanoparticle. Our results can be relevant to the understanding of the catalytic activity of Ag-Pd nanoparticles in those reactions in which subsurface sites play a role.
通过在基于密度泛函理论计算开发的原子势内进行全局优化搜索，研究了具有神奇尺寸的银钯纳米合金中的化学有序性。考虑了面心立方截顶八面体、二十面体和十面体几何结构的富银、中间和富钯成分。除了表面银富集外，我们还发现钯在次表面有显著富集，蒙特卡罗模拟证实这种富集在相当高的温度下仍会持续。这种次表面钯富集在纳米颗粒中比在体相系统中更强，并且根据在银主体纳米颗粒中包含单个钯杂质的能量学进行了解释。我们的结果可能有助于理解银钯纳米颗粒在次表面位点起作用的那些反应中的催化活性。
