大尺寸贵金属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 large-sized noble metal nanoclusters by molecular dynamics simulation

采用分子动力学方法和原子嵌入势模拟了大尺寸金(n=1136～1556)、银(n=1088～1724)、铜(n=1000～1600)、铂(n=1004～1800)原子纳米团簇的熔化过程,得出了相应纳米团簇的势能随温度的变化曲线以及热容量随温度的变化曲线,研究了各种原子纳米团簇熔点与其团簇尺寸的关系.模拟结果表明团簇的熔点随团簇尺寸增大而升高,并逐渐向大块晶体靠拢.所有纳米团簇在熔化过程中在熔点附近都出现负热容现象,通过对团簇熔化前后结构的比较,分析了导致这种现象的原因.

The melting processes of large-sized Au. （n= 1136- 1556）, Ag. （n= 1088 ~ 1724）, Cu. （n= 1000-1600） and Pt.（n=1044-1800） nanoelusters have been studied by molecular dynamics technique with the frame work of EAM. The corresponding curves of potential energy changing with temperature have been gained. The results indicate that the melting points increase almost linearly with cluster＇s size, and approach to bulk erystal＇s gradually. Around melting temperature, all the clusters have negative heat capacity, and the reason has been analyzed.