Competition between Icosahedral Motifs in AgCu, AgNi, and AgCo Nanoalloys: A Combined Atomistic-DFT Study
Competition between Icosahedral Motifs in AgCu, AgNi, and AgCo Nanoalloys: A Combined Atomistic-DFT Study
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DOI：
10.1021/jp410379u
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发表时间：
2013-12-12
影响因子：
3.7
通讯作者：
Ferrando, Riccardo
中科院分区：
文献类型：
--
作者：
Laasonen, Kari;Panizon, Emanuele;Ferrando, Riccardo
AgCu，AgNi和AgCo纳米合金的结构与二十面体几何结构已经计算研究了原子和密度泛函理论（DFT）计算的组合，尺寸高达约1400个原子。这些纳米合金优先假定核-壳化学有序，Ag在壳中。这些核-壳纳米颗粒可以具有中心或偏离中心的核;它们可以在其中心位置具有原子空位或呈现不同的Ag壳排列。在这里，我们比较这些不同的二十面体图案，并确定影响其稳定性的因素，通过局部应变分析。计算发现，偏心的核心是有利的足够大的核心尺寸和中心空位是有利的，在纯Ag团簇，但不是在二元团簇与核心的小尺寸。在大多数情况下，原子理论和密度泛函理论的计算结果吻合得很好，只有五面体-十二面体结构的计算结果存在一定的差异。我们的结果支持原子模型的准确性。还分析了纳米粒子的自旋结构和电荷转移。
The structures of AgCu, AgNi, and AgCo nanoalloys with icosahedral geometry have been computationally studied by a combination of atomistic and density-functional theory (DFT) calculations, for sizes up to about 1400 atoms. These nanoalloys preferentially assume core-shell chemical ordering, with Ag in the shell. These core-shell nanoparticles can have either centered or off-center cores; they can have an atomic vacancy in their central site or present different arrangements of the Ag shell. Here we compare these different icosahedral motifs and determine the factors influencing their stability by means of a local strain analysis. The calculations find that off-center cores are favorable for sufficiently large core sizes and that the central vacancy is favorable in pure Ag clusters but not in binary clusters with cores of small size. A quite good agreement between atomistic and DFT calculations is found in most cases, with some discrepancy only for pentakis-dodecahedral structures. Our results support the accuracy of the atomistic model. Spin structure and charge transfer in the nanoparticles are also analyzed.