AgCo)561团簇升温过程中结构与熔化研究 Study of Structure and Melting for (AgCo)561 Nanoclusters during Heating Process

本文采用分子动力学方法模拟Ag及其掺杂团簇升温过程，通过平均原子势能曲线、团簇快照图分析团簇的结构和熔化行为。研究发现Ag团簇在熔化前出现二十面体结构转变，转变温度随团簇尺寸减小而降低。在(AgCo)561掺杂团簇中，Co原子的数量和位置对团簇结构和性质有重要作用：掺杂Co原子促进(AgCo)561团簇的二十面体结构转变，引起转变温度降低，且掺杂原子数越多二十面体结构转变温度越低；中心掺杂团簇的二十面体结构转变温度最高，而外层掺杂可诱导出无序态异常结构，导致团簇升温无二十面体结构转变；掺杂对团簇熔点有影响，掺杂导致团簇熔点降低，但在中心位置掺杂55个Co原子引起熔点升高。 In this work, the Ag and doping clusters during the heating processes were studied using molecular dynamics simulations. Based on the potential-temperature curves, the snapshots are obtained and the structural transitions and melting behavior are analyzed. Our results show an icosahedral structure change during the heating processes of Ag clusters and the temperature of structure change is decreased with the size reduction of clusters. For doping Ag clusters, we found that the structure and property were influenced by the number and doping position of Co atoms in (AgCo)561 cluster. The structure change temperature of icosahedral is decreased with the increasing Co atoms and increased with center position doping by Co atoms. For a special case, there is an irregular structure by doping Co atoms in outer layer of clusters and the icosahedral structure change is disappear in this cluster. And the melting temperature is decreased by doping Co atoms, but the higher melting temperature is obtained in Co55Ag506 by Co center doping.