物理化学学报 >> 2007, Vol. 23 >> Issue (03): 355-360.doi: 10.3866/PKU.WHXB20070314

研究论文 上一篇    下一篇

氢原子吸附的Cu(100)表面原子结构和电子态

蔡建秋;陶向明;谭明秋   

  1. (温州大学物理与电子信息学院, 浙江 温州 325027; 浙江大学物理系, 杭州 310027)
  • 收稿日期:2006-09-11 修回日期:2006-10-26 发布日期:2007-03-07
  • 通讯作者: 蔡建秋 E-mail:cjaqu@wzu.edu.cn

Atomic Geometry and Adsorption of Cu(100)/H Surface

CAI Jian-Qiu;TAO Xiang-Ming;TAN Ming-Qiu   

  1. (College of Physics and Electronic Information, Wenzhou University, Wenzhou 325027, Zhejiang Province, P. R. China; Department of Physics, Zhejiang University, Hangzhou 310027, P. R. China)
  • Received:2006-09-11 Revised:2006-10-26 Published:2007-03-07
  • Contact: CAI Jian-Qiu E-mail:cjaqu@wzu.edu.cn

摘要: 用密度泛函理论的总能计算研究了金属铜(100)面的表面原子结构以及在不同覆盖度时氢原子的吸附状态. 研究结果表明, 在Cu(100)c(2×2)/H表面体系中, 氢原子吸附的位置是在空洞位置, 距最外层Cu原子层的距离为0.052 nm, 相应的Cu—H键长为0.189 nm, 并通过计算结构参数优化否定了其它的吸附位置模型. 总能计算得出Cu(100)c(2×2)/H表面的功函数为4.47 eV, 氢原子在这一体系的吸附能为2.37 eV(以孤立氢原子为能量参考点). 通过与衬底原子的杂化, 氢原子形成了具有二维特征的氢能带结构, 在费米能级以下约0.8 eV处出现的表面局域态是Cu(S)-H-Cu(S-1)型杂化的结果. 采用Cu(100)表面p(1×1)、p(2×2)和p(3×3)的三种氢吸附结构分别模拟1, 1/4, 1/9的原子单层覆盖度, 计算结果表明, 随着覆盖度的增加, 被吸附的氢原子之间的距离变短, 使得它们之间的静电排斥和静电能增大, 从而导致表面吸附能和吸附H原子与最外层Cu原子间垂直距离(ZH-Cu)逐渐减小. 在较低的覆盖度下, 氢原子对Cu(100)表面的影响主要表现为单个原子吸附作用的形式. 通过总能计算还排除了Cu(100)表面(根号2×2根号2)R45°-2H缺列再构吸附模型的可能性.

关键词: Cu(100)/H表面, 表面吸附态, 密度泛函理论, 覆盖度

Abstract: The structural and adsorption properties of Cu(100)/H surface were studied using density-functional theory (DFT) and projector-augmented wave (PAW) method. It was concluded that atomic hydrogen was adsorbed on the four- fold hollow (FFH) site with a perpendicular distance of 0.052 nm from the outmost Cu layer for a Cu(100)c(2×2)/H geometry. The bond length between H atom and substrate was calculated to be about 0.189 nm. In this adsorbate-substrate system the surface work function was predicted to be about 4.47 eV, which was almost identical to that of a clean Cu(100) surface. The total-energy calculations showed that the chemisorption energy of atomic hydrogen in the case of Cu(100)c(2×2)/H surface was about 2.37 eV with respect to an isolated atomic hydrogen as reference. The hydrogen adsorption on Cu(100) surface yielded the hybridization between surface Cu atoms and adsorbed H, and gener- ated the surface localized states at -0.8 eV relative to Fermi energy EF. This system was modeled at different coverages using p(1×1), p(2×2), and p(3×3) geometries of hydrogen atoms adsorbed on the FFH sites of the Cu(100) surface. The corresponding equilibrium geometries were obtained by total energy and Helleman-Feynman force conjugate-gradient optimizations. In the regime of lower H coverages, the hybridization between adsorbed hydrogen and substrate displayed a type of Cu(S)-H-Cu(S-1) mixing.

Key words: Cu(100)/H surface, Surface chemisorption, Density functional theory, Coverage