不同晶面银纳米晶高温熔化的各向异性

Anisotropy of melting of Ag nanocrystal with different crystallographic planes at high temperature

采用嵌入原子势,使用分子动力学方法,模拟研究了银纳米晶高温弛豫过程中的热稳定性和熔化机制,并引入均方位移和稳定寿命来分析它的结构和形状的演化过程.结果表明:对于沿相互垂直{110},{211}和{111}面切割形成的近正方体截面纳米晶,高温弛豫熔化存在明显的各向异性行为;(1ˉ12)面热稳定性最低,最易熔化,其次是(110)面,热稳定性最高的是(1ˉ1ˉ1)面,最难熔化;三个不同晶面的最外层和次外层原子的稳定寿命极短,且三个不同晶面之间相差很小,没有明显差异;对于具有相同晶面指数的晶面,第三层及其以内的稳定寿命较长,且依次微量增长,但不同晶面第三层及其以内的寿命相差明显.

The thermal-stability and melting mechanism of the Ag nanocrystalline in the process of high-temperature relaxation are investigated with embedded atomic method and molecular dynamics simulations. The dynamic evolution of the crystalline＇s morphology is revealed based on the analyses of mean square displacement and lifetime of the stability. It is concluded that there are obviously anisotropic behaviors in the process of high-temperature relaxation in the quasi-cubic nanocrystal which is cut along the inter-perpendicular facet of {110}, {211} and {111}. The thermal-stability decreases in the sequence of facet （111）, facet （110）, and facet （122）. The lifetimes of the first outmost and the second outmost atoms in those three different facets are extremely short and show no evidently difference from each other. However considering the facets with the same crystal plane indices, the lifetimes are longer within the third atom layer and subtly increase with the increase of the number of atom layers. However, the lifetimes are distinctly different from each other among the three different facets within the third atom layer.