表面原子和小团簇的扩散研究是研究晶体生长和薄膜制备的重要内容之一。表面岛是薄膜生长过程中常见的形貌，从原子尺度研究表面台阶处单个吸附原子以及二聚物的扩散过程对全面理解薄膜的制备过程、实现纳米材料的可控生长有很重要的科学意义。本文结合半经验的EAM势，采用分子动力学静态计算的方法对单个吸附原子(Cu、Ag和Pd)及其相应的二聚物(Cu2、Ag2和Pd2)在Cu表面单层台阶处的扩散势垒进行了计算，探讨了增原子与衬底的互溶与否对扩散势垒的影响，讨论了衬底表面性质与扩散势垒之间的关系，比较了二聚物的扩散势垒与单个吸附原子的扩散势垒的之间的关系，并且由扩散势垒的结果初步预测了二聚物在台阶边缘处的支配扩散机制。

Study on diffusion of adatom and small clusters is one of the key research topics on crystal growth and thin film production. Islands are very common morphologies in such process. This study on the diffusion processes of adatom and dimer at atomic level is of great scientific significance to the understanding of the processes of thin film production, and to the controled growth of nanomaterials.In this paper, we study the diffusion barrier of homogeneous and heterogeneous adatoms (Cu, Ag and Pd) and dimers (Cu2, Ag2, Pd2) on monolayer step edges of copper using static calculation of molecular dynamics simulation. And the interatomic potentials used in this calculation method are described by the embedded-atom potential. We compare the diffusion barrier between adatoms and dimers. We further discuss the impact of the miscibility/immiscibility of adatom and dimer with the substrate on the diffusion barrier. And according to the diffusion barrier of different mechanisms, we predict the dominate mechanism for the dimer diffuse across the monolayer step.In order to understand if it is possible for the adatom that formed on the faceted islands to diffuse upward during homoepitaxy and heteroepitaxy on Cu {110} surface step, we calculate the diffusion barrier when the adatoms cross the surface island via the outter-corner and the inner-corner with the static calculation. Moreover, the effect of the lattice mismatch on the outter-corner diffusion barrier is studied in all the Ag-Cu adatom on Ag {110} surface steps.The conclusions of this work are as follows:1. We studied the diffusion barrier of three different kinds of adatoms and dimers on the Cu surface monolayer step. The conclusions are as follows:1) On all Cu surface monolayer steps, the diffusion barrier of the dimers is larger than that of coresponding adatoms.2) The diffusion barrier for adatom and its dimer to cross {111} surface monolayer step is the lowest. The next is that of crossing {100} surface monolayer step. And that of crossing the asymmetric {110} surface is the highest.3) When dimers diffuse across the surface monolayer step, they are inclined to dissociate. And for Cu2 on Cu substrate and Pd2 (miscible with Cu )on Cu substrate, the domninant diffusion machenism is dissociate exchange, but for Ag2 (none miscible with Cu) on Cu substrate, dissociative jump diffusion dominate. 2. The diffusion barriers of Ag, Cu and Pd adatom diffuse across the steps on Cu {110} surface via outter-corner and inner-corner were calculated, the diffusion barriers of Ag and Cu adatom diffuse across the steps via outter-corner on Ag{110} substrate was calculated too.Now the results are as follows: