AI 中文总结
该研究结合机器学习原子间势的分子动力学模拟与马尔可夫状态模型，发现膦稳定金纳米团簇的晶体结构多为亚稳态，配体覆盖度会调控其结构转变与异构化动力学，指出需将其视为动态集合而非仅静态晶体结构。
AI 中文摘要
原子级精确的膦稳定金纳米团簇通常通过单晶X射线衍射表征，但这些静态结构在多大程度上代表有限温度行为仍不清楚。为探究气相中这些团簇的自由能景观、平衡布居和异构化动力学，我们建立了一个通用框架，将基于机器学习原子间势的分子动力学模拟与马尔可夫状态模型（MSMs）相结合。对MSMs的分析表明，实验报道的晶体结构常对应次要的亚稳态或瞬态构型，而非主导的有限温度结构。配体覆盖度的增加会系统性改变结构重排的热力学和动力学，驱动金核从平面向三维转变，同时加快异构化动力学。此外，催化可及的几何结构通常只是平衡集合中的次要成员，凸显了结构稳定性与表面可及性之间的权衡。这些结果强调，配体保护的纳米团簇需被视为动态集合，其有限温度行为无法仅通过对应的晶体结构完全捕获。
英文摘要
Atomically precise phosphine-stabilized gold nanoclusters are commonly characterized by single-crystal X-ray diffraction, yet the extent to which these static structures represent finite-temperature behavior remains unclear. To explore the free-energy landscapes, equilibrium populations, and isomerization kinetics of these nanoclusters in the gas phase, we establish a general framework that combines molecular dynamics simulations based on a machine-learned interatomic potential with Markov state models (MSMs). Analysis of the MSMs indicates that experimentally reported crystal structures frequently correspond to minor metastable states or transient configurations rather than the dominant finite-temperature structures. Increasing ligand coverage systematically alters both the thermodynamics and kinetics of structural rearrangements, driving the transition from planar to three-dimensional gold cores while accelerating isomerization dynamics. Moreover, catalytically accessible geometries are often only minor members of the equilibrium ensemble, highlighting a trade-off between structural stability and surface accessibility. These results emphasize that ligand-protected nanoclusters need to be viewed as dynamic ensembles and their finite-temperature behavior cannot be fully captured by their corresponding crystallographic structures alone.
Comments26 pages, 5 figures
