银纳米团簇负热容现象的分子动力学模拟

采用分子动力学方法和嵌入原子法(EAM)多体势函数,模拟研究了银纳米团簇在不同温度直到熔化过程中的结构变化,得到了体系能量和热容量随温度的变化关系.结果显示:银纳米团簇在临近熔点附近出现了负热容现象.研究了弛豫后银纳米团簇的稳态结构变化及其在不同时刻结构的演变过程.结果表明:产生负热容现象的主要原因是纳米团簇在熔点附近,结构发生了巨大的变化,形成由{111}和{100}面围成的结构十分稳定和能量更低的多面体.

Molecular dynamics simulation on the negative heat capacities of Ag nanoclusters

Molecular dynamics method and embedded-atom potential are used to study the structure variety of Ag nanoclusters at different temperatures.The curves of the potential energy and the heat capacities changing with temperatures are obtained.It is found that the nanocluster has negative heat capacity around melting temperatures.The structural evolution and the stable structures of Ag nanoclusters at different time are especially studied.The results show that the main reason of the negative heat capacity is the huge variety of the structure.When the temperature is close to the melting point,the Ag cluster forms a polyhedron bounded by {111} and {100} facets,which is very stable.