Aln（n=13-32）团簇熔化行为的分子动力学模拟研究

摘要

Based on the Gupta-type semi-empirical inter-atomic many body potential, the melting properties of Aln(n=13-32) clusters are systematically investigated by using the molecular dynamics method combined with the simulated annealing and quenching techniques. Our results show that, except for several sizes (Al13 and Al19), in general the heat capacity curves all are in disorder (no obvious single-peak), which are consistent with the experimental observations that small aluminum clusters have messy heat capacity curves in the melting process. Reasons for the different melting behaviors (whether they exhibit regular or irregular heat capacity curves) of these small Al clusters can be explored by analyzing the energy distributions of the simulated quenching structures of these clusters at different temperatures. For the clusters with disordered heat capacity curves one can obtain the melting points from analyzing the atomic equivalence indexes of those clusters, and the variations of the calculated melting points of the aluminum clusters with increasing cluster size are in agreement with the experimental observations.%基于半经验的Gupta原子间多体相互作用势，采用分子动力学方法并结合模拟退火及淬火技术，系统研究了小尺寸铝团簇Aln (n=13-32)的熔化行为。模拟结果表明：除个别尺寸(Al13和Al19)外，团簇熔化过程比热曲线普遍呈现杂乱无规(无明显单峰)现象，这与实验观测小Al团簇比热普遍无规的结果完全一致。通过分析不同温度点上团簇淬火构型的势能分布图给出了小Al团簇比热呈现无规或有规现象的成因。对于比热无规团簇，可以利用原子等价指数判断给出团簇熔点，所得团簇熔点随团簇尺寸的变化趋势与实验观测结果完全一致。