液态金属In凝固过程中微观结构转变的模拟研究

采用分子动力学方法对液态金属In的快速凝固过程进行计算机模拟跟踪研究.运用HA键型指 数法和原子成团类型指数法分析了金属原子In的成键类型和形成的原子团簇结构.发现：与通常的液态金属(如Al)相反，随着温度的降低，二十面体及与二十面体相关的1 551 键越来越少；与四方体，六角密堆积相关的1421，1422和1431键数目总和变化很小；而与菱 面体相关的132l，1311，1301和1201的数目却随着温度的降低而显著增加，逐渐占据优势 .最后形成一种新型的以菱面体结构为主、夹杂着立方体(fcc，bcc) 关键词： 液态金属In 微结构转变 团簇结构 分子动力学 计算机模拟

Simulation study of microstructure transition of liquid metal in during solidification processes

A computer simulation tracking study for the rapid solidification processes of liquid metal In system has been performed by means of molecular dynamics method.Using the index method of Honeycutt Andersen(HA)and the cluster bond type index method,the bond types,clusters and cluster configurations of In atoms are analyzed.It has been found that,contrary to conventional metals(such as Al),the relative number of 1551,1541 bond types,related to the icosahedral configuration,is decreased remarkably with decreasing temperature;the total number of 1421,1422 and 1431 bond types,related to the fcc and hcp structures,only changes a little;the total number of 1321,1311,1301 and 1201 bond types,related to the rhombohedral structure,increases remarkably,and then gradually plays a dominant role.Finally,the amorphous structure is formed mainly with rhombohedral structures and mixed up with clusters of cubic(fcc,bcc)and hcp structures.However,the icosahedral and various polyhedra structures,which occupied a dominant position in the previous amorphous structure of metal Al,vanish completely in the present amorphous structure of metal In.This is just the physical origin in microstructure for the obvious difference between the g(r) curves of amorphous In having a splitting second peak with a lower front sub peak and a higher behind one,and the g(r) curves of amorphous Al having a splitting second peak with a higher front sub peak and a lower behind one.