Metal nanocrystals are of considerable scientific interest because of their uses in electronics, catalysis, and spectroscopy, but the mechanisms by which nanocrystals nucleate and grow to achieve selective shapes are poorly understood. Ab initio calculations and experiments have consistently shown that the lowest energy isomers for small silver nanoparticles exhibit two-dimensional (2D) configurations and that a transition into three-dimensional (3D) configurations occurs with the addition of only a few atoms. We parameterized an e-ReaxFF potential for Ag nanoclusters (N ≤ 20 atoms) that accurately reproduces the 2D–3D transition observed between the Ag₅ and Ag₇ clusters. This potential includes a four-body dihedral term that imposes an energetic penalty to 3D structures that is significant for small clusters but is overpowered by the bond energy from out-of-plane Ag–Ag bonds in larger 3D clusters. The potential was fit to data taken from density-functional theory and coupled-cluster calculations and compared to an embedded atom method potential to gauge its quality. We also demonstrate the potential of e-ReaxFF to model redox reactions in silver halides and plasmon motion using molecular dynamics simulations. This is the first case in which e-ReaxFF is used to describe metals. Furthermore, the inclusion of a bond-order dependent dihedral angle in this force field is a unique solution to modeling the 2D–3D transition seen in small metal nanoclusters.

中文翻译：

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银纳米团簇的e-ReaxFF描述的开发和初始应用。

金属纳米晶体由于其在电子学，催化和光谱学中的用途而引起了广泛的科学兴趣，但人们对纳米晶体成核和生长以达到选择形状的机理了解甚少。从头开始的计算和实验一致地表明，小的银纳米粒子的最低能量异构体表现出二维（2D）构型，并且仅添加几个原子就发生了向三维（3D）构型的转变。我们参数为银纳米团簇电子ReaxFF电位（Ñ ≤20个原子），其可精确地再现的Ag之间观察到的2D-3D过渡₅和Ag ₇集群。这种潜力包括一个四体二面角术语，该术语对3D结构施加了能量上的损失，这对于小型簇而言是重要的，但在较大的3D簇中，由于面外Ag-Ag键的键能而被压倒。该电势适合来自密度泛函理论和耦合簇计算的数据，并与嵌入式原子方法电势进行比较以衡量其质量。我们还展示了e-ReaxFF利用分子动力学模拟在卤化银和等离激元运动中模拟氧化还原反应的潜力。这是第一种使用e-ReaxFF来描述金属的情况。此外，在此力场中包含键序相关的二面角是模拟小型金属纳米团簇中2D–3D过渡的独特解决方案。