纳米Cu颗粒等温晶化过程的分子动力学模拟研究

采用分子动力学方法和镶嵌原子势,模拟了500个Cu原子(简称Cu₅₀₀) 组成的纳米颗粒的等温晶化过程.利用修正的均方位移、键对分析技术和内在结构(IS) 等方法对该过程中的结构和动力学行为进行分析研究.结果显示:与块体金属不同的是, Cu₅₀₀纳米颗粒在某一温度保温时,其晶化时间并不是一个定值, 而是存在一个统计分布,并且保温温度越低其晶化时间的分布范围越广, 最长晶化时间越长.在低温晶化时, Cu₅₀₀经历了一系列中间构型的转变才达到晶态, 表现出多步晶化的特征.文章作者研究了颗粒的初始构型对晶化进程的影响, 发现颗粒的初始结构特征和能量状态对其随后的晶化过程有着重要的影响, 同一温度下,颗粒初始构型的IS能量越低其晶化时间越长,这一点在低温时尤其明显.

Molecular dynamics simulation of isothermal crystallization dynamics in Cu nanocluster

We investigate the structural and dynamic properties of isothermal crystallization of Cu nanocluster which contains 500 Cu atoms (Cu₅₀₀), according to the embedded atom model, using molecular dynamics simulations. We calculate the Honeycutt-Anderson bond-type index, the inherent structure (IS) and the revisionary mean-square displacement of Cu nanocluster in crystallization process. All analyses suggest that the crystallization time of Cu₅₀₀ is dependent on temperature. At high temperature, the crystallization time is well represented by a Gaussian distribution, which is not observed at low temperature. Cu₅₀₀ displays multi-step crystallization at low temperature. On the other hand, we note that the influence of initial configuration on isothermal crystallization is significant. For the same thermodynamic state, especially at low temperature, the lower the IS of initial configuration, the longer the crystallization time is.