替位杂质对贵金属(111)表面稳定性影响的分子动力学研究

Study on the influence of substitutional impurity on the stability of noble metal (111) surfaces by molecular dynamics simulation

采用嵌入原子方法的原子间相互作用势,通过分子动力学方法研究了过渡族金属Cu,Ag,Au,Ni,Pd,Pt(111)表面的相互替位掺杂对表面稳定性的影响,计算了替位掺杂体系的表面能与表面空位形成能,探讨了影响表面稳定性的因素及其变化规律.计算表明替位杂质对表面能变化的影响主要是替位杂质的凝聚能和原子半径,而影响空位形成能变化的原因除凝聚能和原子半径外,合金溶解热具有重要的作用.此外,通过替位杂质导致的体系表面能变化对合金体系的偏析行为进行了预测,理论预测与实验结果符合很好.

The stability of noble metal （111） surfaces doped with substitutional impurities were studied by molecular dynamics simulation. The atomic interaction potentials with the embedded atom method were applied in the simulation. The change of surface energy and the formation energy of surface vacancy induced by substitutional impurity were calculated. We found that the main factors effecting the surface energy of noble metal （111） surfaces are the cohesive energy and atomic radius of the substitutional impurity. The heat of solution of the binary alloy also has an important role in the influence of substitutional impurity on the formation energy of surface vacancy, along with the cohesive energy and atomic radius of substitutional impurity. Furthermore, the change of surface energy induced by substitutional impurity was used to predict the segregation of the binary alloy in the surface theoretically, yielding good agreement with the experimental results obtained by others.