铜原子纳米团簇热力学性质的分子动力学模拟研究

Study on the thermodynamic properties of Cu_N nanoclusters by molecular dynamics simulation

利用分子动力学模拟方法,研究了CuN(N=80,140,216,312,408,500,628和736)纳米团簇在热化和冷凝过程中结构和热力学性质的变化,模型采用的是Johnson的EAM作用势.模拟结果表明:铜团簇的熔点和凝固点随其尺寸线性增加,并逐渐向大块晶体靠拢;所有团簇的凝固点都低于熔点,出现凝固过程中的滞后现象;在熔点和凝固点附近,团簇都具有负热容特性,负热容是由相变前后团簇内部结构突变引起的.

The thermodynamic properties of CuN（N=80, 140, 216, 312, 408, 500, 628 and 736） nanoclusters during melting and freezing processes have been studied by molecular dynamics simulation technique within the framework of EAM. The results indicates that the melting and freezing points of CuN nanoclusters increase linearly with size, and approach to bulk crystal＇s gradually. For the same cluster, the freezing point is lower than its melting point. Hysteresis in the melting/freezing transition is observed. All the nanoclusters have negative heat capacity around the melting and freezing points, which is generated by the abrupt structure jump.