熔融Cu_(57)团簇在急冷过程中弛豫和局域结构转变的分子动力学研究  

Molecular dynamics study of relaxation and local structure changes in a rapidly quenched molten Cu_(57) cluster

作　　者：樊沁娜[1] 李蔚[1] 张林[1] 

机构地区：[1]东北大学理学院,沈阳110004

出　　处：《物理学报》2010年第4期2428-2433,共6页Acta Physica Sinica

基　　金：国家重点基础研究发展计划(批准号:G2006CB605103)资助的课题~~

摘　　要：采用基于嵌入原子方法的正则系综分子动力学研究熔融Cu57团簇在急冷过程中的弛豫及其局域结构变化.通过对弛豫过程中均方位移、非相干中间散射函数和非Gauss参数三种函数和原子键对随急冷温度不同所发生变化的分析表明,在经过短时间的原子剧烈运动后,急冷温度极大地影响着团簇内原子结构弛豫过程.急冷温度较高时,原子在经历短时间剧烈运动的β弛豫后,进入α弛豫区后以扩散运动为主,随后原子运动表现为非扩散性的原子局域结构重排,团簇内没有出现明显的成核结构.随着温度的降低,原子局域结构的变化在经过短时间原子剧烈运动的β弛豫后,在α弛豫区原子运动表现为扩散性运动,并出现一定数量的不稳定二十面体结构.当急冷温度很低时,在进入α弛豫区后,团簇结构变化逐渐表现为非扩散性原子局域结构重排,形成相当数量的稳定成核二十面体结构.Relaxation and local structure changes of a molten Cu57 cluster during rapidly quenching have been studied by molecular dynamics simulation using embedded atom method.With decreasing quenching temperature,atom motion details are analyzed using three factors,including the mean square displacement,incoherent intermediate scattering function,and non-Gaussian parameter,while the local structure changes are identified by pair analysis.Simulation results reveal that after a drastic collective motion of atoms,the temperature greatly affects the relaxation processes of the cooled cluster.At a high quenching temperature,after atoms dramatically move in a β relaxation region,diffusion motion of the atoms plays a dominant roles followed by non-diffusion rearrangements of local atomic structures,and no nucleation occurs.When the temperature decreases,local structure changes of atoms occur as the initial dramatic motion,then through the diffusion of atoms in the α relaxation region,and some unstable icosahedral structures are observed.At a low quenching temperature,the structure changes in the α relaxation region result mainly from non-diffusion rearrangement of the atom positions,and a notable amount of icosahedral structures are formed.

关 键 词：团簇 分子动力学 计算机模拟 表面 

分 类 号：O561[理学—原子与分子物理]