中介尺度Au纳米团簇熔化的分子动力学模拟

Melting of Au Nanoclusters by Molecular Dynamics Simulation

采用分子动力学模拟技术,研究了原子个数为16～8628的Au纳米团簇的熔化过程.采用Johnson的EAM(embeddedatommethod)模型,模拟结果表明,金属纳米团簇存在一中介尺度区域.对Au纳米团簇而言,当原子个数N>456时,团簇的热力学性质与团簇尺寸呈线性关系,熔化首先从表面开始,逐步向中心区域推进,且满足Tmb-Tmc(N)=aN(-1/3)的关系.另外,计算了中介区域的团簇的尺寸、熔化温度、表面能、熵、焓等热力学量以及均方根位移(RMSD)等动力学量,为研究纳米团簇提供定量数据.

We present a detailed molecular dynamics study of the melting of Au nanoclusters with up to 8628 atoms within the framework of the embedded atom method(EAM). The simulation indicates that there exists a mesoscale nanocrystal regime in metal nanoclusters. The predicted thermodynamics properties for Au nanoclusters above 456 atoms show a linear dependence on the cluster size, whereas the melting begins from the surface of the clusters with a melting point at T-m(b) - T-m(c) (N) = aN((-1/3)). In addition, the cluster size, surface energy as well as the average root-mean-square displacement (RMSD) of the clusters in the intermediate regime have been investigated.