( 1. 中南大学 材料科学与工程学院, 长沙 410083;
2. 江苏大学 材料科学与工程学院， 镇江 212013)
摘 要: 利用分子动力学研究了原子数为13～1 055的铜纳米团簇。 结果表明： 随着尺寸的减小， 铜纳米团簇的结构发生晶体→非晶→晶体→非晶→晶体→非晶的转变。 团簇平均原子结合能随着尺寸的减小而减小， 且只依赖于短程有序， 这说明了团簇平均原子结合能一般不能够作为非晶与密堆结构晶体转变的判据。 平均原子间距不但依赖于团簇的尺寸， 且对团簇结构的变化敏感， 可以作为非晶与密堆结构晶体转变的一个判据。 对偶分布函数的研究表明， 大尺寸团簇的内部和表层原子结构都表现出晶格收缩效应, 且不同于相应块体晶格， 这表明了目前文献中关于团簇的块体加表面模型与壳核模型都有待改进。
关键字: 分子动力学； 铜团簇； 结合能； 平均原子间距
（ 1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. School of Materials Science and Engineering, Jiangsu University,
Zhenjiang 212013, China）
Abstract: The Cu nanoclusters with atom number of 13-1 055 have been studied by molecular dynamics simulation method. The results show that the structure of Cu nanoclusters follows the sequence of crystalline→amorphous→crystalline→ amorphous→crystalline→amorphous with the decrease of the cluster size. The average atom cohesive energy decreases with the decrease of the cluster size, and only depends on the short-range order, which shows that the mean atom cohesive energy can not be regarded as the criterion of determining the structure of amorphous and close packed crystallines. However, the mean atom distance depends on not only the cluster size, but also the cluster structure, which can be regarded as the criterion of determining the structure transformation. Furthermore, the study on pair correlation function shows that both the interior and outer shells of the larger clusters contract a little, and are different from those of the corresponding bulk crystal, which suggests that the present bulk-surface and core-shell models of clusters should be improved.
Key words: molecular dynamics; Cu nanoclusters; cohesive energy; mean atom distance
