摘要
用密度泛函理论(DFT)的广义梯度近似(GGA)方法对钠原子在银(001)面吸附的性质进行了理论研究.计算表明,钠原子吸附在银(001)面空位最稳定,桥位次之,而顶位吸附能量最高;优化得到的吸附结构几何参数与实验测定结果吻合.对3种吸附结构的电子结构和局域态密度分析表明,钠原子吸附到银表面后,其电子将部分转移到金属表面,导致银的费米能级上升,化学活性增强.通过比较氢气分子在洁净银表面和吸附了钠的银表面进行的裂解反应活性证实,金属钠吸附在银表面表现出明显的助催化作用.
The properties and geometries of Na atoms adsorption on Ag （001） surface were studied by means of the density functional theory （DFT） with the generalized gradient approximation （GGA）. The adsorption energies, adsorption structures and density of states were calculated at O. 25 monolayer （ML）.It was found that the hollow sites were the favorable adsorption sites with the lowest adsorption energies, which was in good agreement with the available experiments. The Fermi level of Ag increased due to elec- trons transferred from Na atoms to silver surface. This result indicated that the chemical activities of the Ag atoms used as catalyst increased, which means partial density of states suggested that the electron that Na is a promoter of catalyst. The results from the of Na atoms entered the p orbital of Ag atoms. At last,the mechanism that Na as a promoter of catalyst was elucidated using an adsorptive hydrogen molecule on the silver surface.
出处
《西南大学学报（自然科学版）》
CAS
CSCD
北大核心
2008年第5期84-89,共6页
Journal of Southwest University(Natural Science Edition)
基金
重庆市自然科学基金资助项目(CSTC-2004BA4024)
关键词
密度泛函理论
表面吸附
态密度
助催化
钠
银
density functional theory
surface adsorption
density of states
promoter of catalyst
sodium
silver
