Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146Genova, Italia.
Université de Limoges, CNRS, IRCER, UMR 7315, F-87000Limoges, France.
ACS Nano. 2023 Jan 10;17(1):587-596. doi: 10.1021/acsnano.2c09741. Epub 2022 Dec 20.
The solidification of AgCo, AgNi, and AgCu nanodroplets is studied by molecular dynamics simulations in the size range of 2-8 nm. All these systems tend to phase separate in the bulk solid with surface segregation of Ag. Despite these similarities, the simulations reveal clear differences in the solidification pathways. AgCo and AgNi already separate in the liquid phase, and they solidify in configurations close to equilibrium. They can show a two-step solidification process in which Co-/Ni-rich parts solidify at higher temperatures than the Ag-rich part. AgCu does not separate in the liquid and solidifies in one step, thereby remaining in a kinetically trapped state down to room temperature. The solidification mechanisms and the size dependence of the solidification temperatures are analyzed, finding qualitatively different behaviors in AgCo/AgNi compared to AgCu. These differences are rationalized by an analytical model.
通过在 2-8nm 尺寸范围内的分子动力学模拟研究了 AgCo、AgNi 和 AgCu 纳米液滴的凝固过程。在体相中，所有这些体系都倾向于发生相分离，表面会出现 Ag 的偏析。尽管存在这些相似之处，但模拟揭示了凝固途径的明显差异。AgCo 和 AgNi 在液相中已经分离，它们在接近平衡的构型中凝固。它们可以显示出两步凝固过程，其中富 Co-/Ni 部分在比富 Ag 部分更高的温度下凝固。AgCu 在液相中不分离，一步凝固，因此在室温下仍处于动力学捕获状态。分析了凝固机制和凝固温度的尺寸依赖性，发现 AgCo/AgNi 的行为与 AgCu 有质的不同。通过一个分析模型对这些差异进行了合理化解释。
