[论文解读] Coexistence of close packed structures in large substrate-free Ar-Kr clusters according to THEED data

O. G. Danylchenko, O. P. Konotop|arXiv (Cornell University)|Jan 5, 2026

nanoparticles nucleation surface interactions被引用 0

一句话总结

该论文分析由绝热膨胀形成的Ar-Kr簇，显示大簇呈现两相fcc-hcp结构且两相成分浓度相等、与成分无关，hcp组分随簇大小增长，在等摩尔组成达到峰值。

ABSTRACT

A quantitative phase analysis of substrate-free single-component and binary clusters of the Ar-Kr system obtained by adiabatic expansion of gas into vacuum through a supersonic nozzle was performed. The studies were carried out in-situ using transmission electron diffraction technique (THEED) on clusters with an average size ranging from 2000 to 100000 atoms/cluster and across the entire range of component concentrations. The independence of the threshold size of clusters, corresponding to the beginning of the formation of the hcp phase, from the component composition was revealed. It was established that clusters larger than this threshold size have a two-phase fcc-hcp structure with an identical concentration of components in each phase. The fraction of the hexagonal phase increases with the size of the aggregations and depends on the component content, reaching maximum in clusters with an equimolar composition. Arguments are presented in favor of the formation of two-phase clusters in the supersonic jet, rather than separate single-phase fcc and hcp ones. These findings are in good agreement with the previously proposed thermally activated diffusion mechanism for the nucleation and growth of the hcp phase in rare gas clusters.

研究动机与目标

• 确定Ar-Kr簇中形成hcp相的簇大小阈值是否依赖于组分组成。
• 表征大型无基底Ar-Kr簇中的结构共存与相分布（fcc和hcp）。
• 评估超音速射流中是否形成两相簇，而非单相fcc与hcp簇的混合。
• 将相分数与整体簇大小和组成相关联，以检验热激活扩散机制对hcp成核的影响。

提出的方法

• 使用透射电子衍射（THEED）在无基底Ar-Kr簇上进行原位定量相分析。
• 簇通过超音速喷嘴将气体膨胀到真空中产生，簇大小范围为2000–100000原子。
• 在整个范围内系统地改变总体组分浓度。
• 分析聚焦于确定相组成（fcc与hcp）及其对大小和组成的依赖性。

实验结果

研究问题

• RQ1 初始hcp相的阈值簇大小是否依赖于簇的Ar-Kr组成？
• RQ2 大型Ar-Kr簇是否以相同组分浓度在fcc与hcp之间呈现两相共存？
• RQ3 hcp六方相分数如何随簇大小和Ar/Kr组成变化？
• RQ4 在超音速射流中形成的两相簇是否更符合成核机制，而非单独的fcc和hcp簇混合？

主要发现

• hcp形成的阈值大小与组分组成无关。
• 比阈值更大的簇显示出两相fcc-hcp结构，且每相中的组分浓度相同。
• 六方相分随簇大小增加并依赖组分含量，在等摩尔簇中达到最大值。
• 论据支持超音速射流中形成两相簇，而非单相fcc和hcp簇的混合。
• 结果与热激活的扩散机制在稀有气体簇中对hcp成核与生长相一致。