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Study on the Process of the Structural Relaxation of Vacancy Clusters by the Visualizing Method with an MD Simulation

MD模拟可视化方法研究空位团簇的结构松弛过程

基本信息

批准号：
11650688
负责人：
NISHIGUCHI Rieko
金额：
$ 1.22万
依托单位：
Hiroshima Jogakuin University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

Computer simulations of molecular dynamics (MD) were used to study the clustering of vacancies in nickel. This is to investigate the atomistic processes of vacancy agglomeration in irradiated metals. First, PKA cross section was calculated to know how many Frenkel pairs form by an irradiation experiment. Next, simulations were carried out with DYNAMO ver. 8.5 code by implementing the potential of the embedded atom method (EAM). First, the perfect crystal was thermalized at 1300K, 1500K, 1700K and 1800K.Then, four triangular vacancy clusters whose sizes were 10 were introduced on (111) planes at randomly selected positions. MD simulations were performed in a very small time step of outputs to observe the atomistic processes of the movement of a vacancy. It was found that vacancy clusters moved and agglomerated with keeping the cluster. Thus a vacancy did not evaporate from a cluster to be absorbed in a larger cluster. There were three different processes in an agglomeration of vacancy clusters. One was an atom caged in a tetrahedral structure of vacancies moved to another lattice site. Another was an atom caged in a hexahedral structure of vacancies moved to another lattice site. The other was an atom moved along a <110> row. The migration energy was 1.13eV(=E_m) for a single vacancy and 0.4eV for a small vacancy cluster (3v). The binding energy of 17v cluster and a single vacancy was 0.8eV=E_b. So the energy for a single vacancy to evaporate from a cluster was E_m+E_b=1.93eV.Therefore it means that a vacancy does not evaporate from a cluster.

采用分子动力学（MD）的计算机模拟方法研究了镍中空位的成簇行为。本文研究辐照金属中空位凝聚的原子过程。首先，计算PKA截面，以了解辐照实验中有多少对Frenkel对形成。接下来，使用CNOMO ver进行模拟。8.5代码通过实现嵌入原子方法（EAM）的潜力。首先在1300K、1500K、1700K和1800K对完整晶体进行热处理，然后在（111）晶面上任意位置引入4个尺寸为10的三角形空位团簇。在很小的输出时间步长内进行MD模拟，观察空位运动的原子过程。结果表明，空位团在保持团簇的情况下发生了移动和聚集。因此，空位不会从团簇中蒸发而被更大的团簇吸收。空位团的聚集过程有三个不同的过程。一种是笼在四面体结构中的原子，空位移动到另一个晶格位置。另一种是被囚禁在空位六面体结构中的原子移动到另一个晶格位置。另一个是一个原子沿着沿着移动。<110>单空位的迁移能为1.13eV（= E_m），小空位团的迁移能为0.4eV（3v）。17v团簇与单个空位的结合能为0.8eV = E_B。因此，单个空位从团簇中蒸发的能量为E_m + E_B = 1.93 eV。