摘要
采用分子动力学方法 ,对含有 10 5个Al原子的液态金属大系统在快凝过程中团簇结构的形成特性进行了模拟研究 ,并采用原子团类型指数法 (CTIM )来描述各种类型的团簇结构组态 .研究结果显示 ,二十面体原子团 (12 0 12 0 )及其组合在微观结构转变中起着最重要的作用 .发现纳米级大团簇 (含有 10 4个原子 )是由一些中等原子团相互结合而成 ,而中等原子团又是由基本原子团结合组成 .这种结构与由热蒸发、离子溅射等方法所获得的以某一个原子为中心、按八面体结构堆积起来的多壳层晶体结构的纳米级大团簇完全不同 .组成这种大团簇结构的基本原子团的中心原子是彼此以单线或扭结的形式相互成键连接的 .这种结构的角隅正好可以成为液态金属凝固过程中形成支晶的起点 .
A simulation study on the formation characteristics of clusters in a large-scale liquid Al system consisting of 105 atoms has been performed by the molecular dynamics method. And a cluster-type index method (CTIM) has been used to describe the structural configurations of various clusters. The results demonstrate that the icosahedron clusters (12 0 12 0) and their combinations play the most important role in the microstructure transition. The nano-clusters (containing up to 104 atoms) have been formed by combining some middle clusters which have been formed by combining smaller basic clusters. The structures of these nano-clusters are very different from those of nano-clusters obtained by evaporation, ionic spray methods, and so on. The latter is formed by the multi-shell crystals accumulated with an atom as the center and the surrounding atoms arranged according to octahedron configuration. The center atoms of these basic clusters are bond-connected each other with the linear or twisting mode. The corners of the nano-cluster just could become the starting points of the dendrite growth in the solidification processes of liquid metals.
基金
ProjectsupportedbytheNationalNaturalScienceFoundationofChina (5 0 0 710 2 1
5 0 2 710 2 6 ) .
关键词
液态金属
快凝过程
纳米团簇结构
计算机模拟
Liquid metal, Rapid solidification process, Nano-cluster configuration, Computer simulation
