摘要
应用EAM模型研究了氢在Ni(511)面的吸附和解离.首先计算了单个氢原子在Ni(511)面上的吸附能、吸附键长及吸附高度,发现氢在Ni(511)面上有三种相对稳定的吸附位,即台阶棱上的二重桥位B、台阶面上的三重洞位H3′以及平台面上的四重洞位H1和H2.与Ni(001)低指数面相比,明显的增加了台阶棱上的二重桥位B以及台阶面上的三重洞位H3′,并且H1位的吸附性也有所增强,说明台阶的存在影响了氢在Ni(511)表面的吸附性,使台阶附近的吸附位增多且吸附性增强;然后计算了氢分子在台阶表面上解离吸附时的活化势垒、吸附能、氢镍之间键长及氢氢之间的距离,计算结果表明台阶底部更易于使氢分子解离,台阶附近是氢吸附和解离的活性部位.
The adsorption and dissociation of hydrogen on stepped surface （511） of nickel are studied with the embedded-atom model （EAM） method. The adsorption energy, the length of the adsorption bond and the adsorption height for a single hydrogen atom are calculated. Three kinds of stable sites are found for hydrogen adsorption. There are the double-fold bridge site B on the step edge, the three-fold hollow site H3＇ on the step surface and the four-fold hollow sites H1 and H2 on the terrace surface. Compared with a hydrogen atom adsorbed on low-index （001） surface, there are two other adsorption sites near the step： the two-fold bridge site B on the step edge and the three-fold hollow site H3＇ on the step surface. At the same time, the absorbability of the hydrogen atom at the site H1 is intensified. The results show that hydrogen adsorption on Ni （511） is affected by the existence of the step. The active barriers, adsorption energy and corresponding bond length for dissociation of a hydrogen molecule on the stepped surface are presented. The results show that the dissociation is easier at the bottom of the step. It is shown that the steps are the active sites for hydrogen adsorption and dissociation.
基金
ProjectsupportedbytheNationalNaturalScienceFoundationofChina(20403004)andHunanProvincialNaturalScienceFoundationofChina(03JJY3011).
关键词
表面吸附
台阶表面
氢
嵌入原子模型
Surface adsorption, Stepped surface, Hydrogen, Embedded-atom model
