In this study, molecular dynamics simulation was used to investigate the effects of nanocluster size and its composition on the thermodynamic stability and structural evolutions of icosahedral Pd@Au@Pd three-shell nanoalloys. It was concluded that the thermal stability of Pd@Au@Pd nanoalloys is significantly dependent on their size and composition in such a way that the increase of nanoparticle size and the decrease of its Au concentration leads to the increase of its melting point. Also, the total mechanism of melting does not depend on nanoparticle size and its composition. The melting process starts from the surface of the nanocluster and leads to the segregation of Au atoms on the surface and the aggregation of Pd atoms in the core region. The final stable structure after the melting point is dependent on the nanoparticle size. For small nanoclusters, a Janus-like structure is formed after the melting point. However, for larger nanoclusters there is a competition between Janus-like and core–shell structures and after the creation of an unstable dumbbell-like intermediate structure, a stable Pd@Au core–shell structure is obtained after the melting point.

中文翻译：

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Pd @ Au @ Pd三壳纳米合金中的哑铃状，核-壳状和Janus状构型：分子动力学研究

在这项研究中，使用分子动力学模拟研究了纳米簇的大小及其组成对二十面体Pd @ Au @ Pd三壳纳米合金的热力学稳定性和结构演变的影响。结论是，Pd @ Au @ Pd纳米合金的热稳定性很大程度上取决于其尺寸和组成，即纳米颗粒尺寸的增加和其Au浓度的降低会导致其熔点的增加。同样，熔化的总机理也不取决于纳米颗粒的大小及其组成。熔化过程从纳米团簇的表面开始，并导致表面上的Au原子偏析和核心区域中Pd原子的凝聚。熔点后的最终稳定结构取决于纳米颗粒的大小。对于小的纳米团簇，在熔点之后形成Janus状结构。但是，对于较大的纳米团簇，Janus型结构和核-壳结构之间存在竞争，并且在创建不稳定的哑铃状中间结构后，在熔点后可获得稳定的Pd @ Au核-壳结构。