液态金属Cu快速凝固过程中原子团簇及非晶态结构转变特性的模拟研究

A simulation study on configurations of clusters and properties of amorphous transition in liquid metal Cu during rapid solidification processes

本文采用Quantum Sutton-Chen多体势,对由5万个液态金属Cu原子组成系统的原子团簇的形成与演变特性进行了分子动力学模似研究.我们采用原子团类型指数法(CTIM)来描述复杂的微观结构转变.研究发现:系统形成以1551、1541和1431三种键型为主的非晶态结构;二十面体原子团(12 0 12 0)和(12 2 8 2)、(13 1 10 2)、(13 3 6 4)、(14 1 10 3)、(14 2 8 4)、(14 3 6 5)缺陷多面体基本原子团在液态转变为非晶体过程中起着关键性的作用.系统所形成的纳米团簇是由一些基本团簇和由这些基本团簇相互连接而成的中等团簇所组成,这正是与由气相沉积法和离子溅射法所获得的团簇结构的本质差别所在.通过双体分布函数g(r)、HA键型、基本原子团、平均原子体积和比值g_(min)/g_(max)的分析,还得到液态金属Cu在冷却速率为1.0×10^(14)K/S时的非晶转变温度T_8约为673 K.同时还发现,1551、1441、1661三种键型随温度有相同的变化趋势,这反映出体系对称性结构有相同的变化规律.

Based on the quantum Sutton-Chen many-body potential, a molecular dynamics simulations study has been performed to investigate the formation and evolution features of clusters in liquid metal Cu system consisting of 50000 atoms. The cluster-type index method （CTIM） was used to describe the complex microstructure transitions. It is demonstrated that the amorphous structures are mainly formed with the three bond-types of 1551,1541 and 1431 in the system; and the icosahedral cluster （12 0 12 0） and other basic polyhedra clusters of （12 2 8 2）,（13 1 10 2）,（13 3 6 4）,（14 1 10 3）,（14 2 8 4） and （14 3 6 5） play a critical and leading role in the transition from liquid to glass. The nano-clusters formed in the system are consisted of some basic clusters and middle cluster configurations by connecting to each other, and distinguished from those obtained by gaseous deposition and ionic spray. By analyzing pair distribution function g（r） curve,HA bond-types,basic cluster-types,Mean volume per atom and ratio of gmin/g it is found that the glass transition temperature Tg for liquid metal Cu is about 673 K at the cooling rate of 1.0 × 10 14 K/s. Meanwhile,it is still found that there are same varied tensions for the 1551.1441,1661 Bond-types with temperature, this reflects that the symmetric configuration in this system has same the varying rlue.