不同势下铱团簇结构和熔化行为的分子动力学模拟

Molecular dynamics simulation of structures and melting behaviours of iridium clusters with different potentials

采用分子动力学方法及淬火技术,结合Gupta势和Sutton-Chen势,模拟研究了包含13,14,55,56,147及148个原子数的铱团簇的熔化行为.结果表明,Gupta势和Sutton-Chen势对所研究的Ir团簇的基态几何结构和熔化行为给出了基本一致的描述:两种不同势给出了完全相同的基态几何结构;两种势给出的Ir团簇熔点及预熔化区间随团簇尺寸的变化关系基本一致;对于小Irn团簇(n=13,14)两类势均表现出比热峰值相对于均方根键长涨落饱和值滞后的现象.但是,包含相同原子数的Ir团簇在Gupta势下的熔点均高于在Sutton-Chen势下的熔点,出现该区别的主要原因是Gupta势所给出的包含相同原子数的Ir团簇基态与第一激发态的能量差均高于在Sutton-Chen势下的相应值.

The molecular dynamics method and quenching technique combined with the Gupta potential and the Sutton-Chen potential are used to study the melting properties of Irn （ n = 13, 14, 55, 56, 147 and 148） clusters. Our results show that the structures and melting behaviors of these clusters described by beth potentials are generally in agreement with each other： the same ground state geometrical structure and the same trend of variation of the melting point and the pre-mehing interval with cluster size are obtained for beth potentials, and for the small Irn （ n = 13,14） clusters, the peak value of heat capacity is delayed from the saturation value of Lindemann index. While, for each of these iridium clusters, the melting point from the Gupta potential is higher than that from the Sutton-Chen potential, and we attribute the main reason to the higher energy gaps between the ground state and the first excited state of these iridium clusters from the Gupta potential than those from the Sutton-Chen potential.