小尺寸金属团簇熔化过程的分子动力学模拟

运用分子动力学方法模拟了小尺寸金属团簇的熔化过程, 原子之间的作用采用嵌入原子法(EAM)模型, 计算了均方根键长涨落δ随温度的变化, 以及升温过程中团簇热容的变化. 包含55、56个原子的面心立方(FCC)结构Au团簇的熔化过程是基本相同的. 而同样结构和数目Cu团簇的熔化过程却呈现出不同的趋势. Cu55、Cu56在模拟过程中都出现了FCC结构到二十面体结构的转变. 但由于表面多出了一个原子, Cu56的热容曲线比Cu55多了一个峰, 体系出现了预熔化现象. 这表明小尺寸团簇的固液转变的过程与团簇的原子类型、几何结构和原子数目密切相关.

Molecular Dynamics Simulation on Melting of Metal Cluster with Small Size

The melting processes of little size metal clusters were simulated by molecular dynamics method. The atomic interaction was described by embedded atommethod (EAM). The root-mean-square (rms) bond length fluctuation and heat capacity versus temperature in heating were calculated. The melting processes of face centered cubic (FCC) Au clusters with 55 and 56 atoms are very similar. But those FCCCu clusters with same size show different trends. Cu55 and Cu56 clusters have structure transitions from FCC structures to icosahedrons during heating processes. Due to one more atom than Cu55 on surface, Cu56 has a pre-melting process. The heat capacity curve of Cu56 has also one more peak than that of Cu55. All the results show that the small cluster’s solid-liquid transition of the small clusters depends on atomtype, structure, and atomnumber of the cluster.