fcc金属表面能的各向异性分析及表面偏析的预测

摘要

本文将元素变量(φ*和nWS)和MAEAM相结合,从原子尺度上对10种fcc金属Cu,Ag,Au,Ni,Pd,Pt,Rh,Al,Ir和Pb的38个不同晶面的表面能进行模拟计算及各向异性分析.结果表明,fcc金属的密排面(111)的表面能最小,则该晶粒取向优先生长,与实验结果和第一原理的LMTO-ASA计算结果一致;各个晶面的表面能均随着其他晶面与(111)晶面的夹角cosθ(hkl)的增长而呈线性增长关系,因此利用(111)面可推导出其他各面的表面能量.并利用图解法解释了表面能与表面偏析能之间的关系,得到具有较低表面能的杂质(溶质)才会偏析到具有较高表面能的基体(溶剂)的表面,产生表面偏析现象这一结论.%In the atomic scale, the surface energy anisotropy analysis of 38 surface planes of 10 fcc metals Cu, Ag, Au, Ni,Pd, Pt, Rh, Al, Ir and Pb have been simulated by using the elemental variables (の)* and nws and modified analytical embedded-atom method (MAEAM). The results show that the close-packed surface ( 111 ) of fcc metals which have the lowest surface energies will grow preferentially, the surface energies for all the other surface planes increase linearly with cosθ(hkl), where cosθ(hkl) are the angles between the surface planes (hkl) and (111), which is consistent with the experimental and the linear-muffin-tin-orbital atomic-sphere approximation (LMTO -ASA) results. A graphical approach which correctly explains the relation of the surface segregation energy and surface energy is employed. We conclude that the surface segregation takes place or not is mainly determined by the rule that an impurity (solute) with lower surface energy will segregate to the surface of the host (solution) with higher surface energy.