核-壳结构Ag-Au纳米颗粒合金化行为的分子动力学

Simulation for Alloying Behavior of Core-Shell Structured Ag-Au Nanoparticles with Molecular Dynamics

摘要:

利用分子动力学方法和改进分析型嵌入原子势函数模拟了核-壳结构Ag-Au纳米颗粒的合金化行为，从原子扩散、微观结构演变以及合金化程度等方面对比分析了壳层厚度对合金化行为的影响。结果表明，壳层较薄时，核-壳界面处原子扩散现象显著，内核表现出多面体形貌，表层Au、Ag原子完全混合。壳层较厚时，表面原子以扩散为主，整个颗粒表面为多面体结构，但内核保持初始球状结构。通过层错生长方式使形貌发生了改变。壳层越薄，体系合金化程度越高

Abstract:

Bimetallic nanoparticles (NPs) have become one of hot spots in materials science due to their unique physical and chemical properties. The alloying process of core-shell structured Ag-Au NPs has been investigated with a modified analytic embedded atom method (MAEAM) and molecular dynamics. The influence of shell thickness on alloying behavior has been studied from the viewpoint of atomic diffusion, microstructure evolution and alloying extent. For NPs with a thin shell, there is a significant atomic diffusion at the core/shell interface. The Ag core undergoes a shape evolution from initial spherical to polyhedron. The surface Au and Ag atoms are fully mixed. For NPs with a thick shell, the atomic diffusion is mainly located to the surface of NPs. The NPs exhibit polyhedron morphology with the Ag core almost unchanged. The morphology above is changed through the stacking fault growth. Compared with the thick shell, the alloying extent of NPs with a thin shell is much greater