物理化学学报 >> 2006, Vol. 22 >> Issue (04): 445-450.doi: 10.3866/PKU.WHXB20060411

研究论文 上一篇    下一篇

氢原子在Ti(0001)表面吸附的密度泛函理论研究

陈文斌;陶向明;赵新新;谭明秋   

  1. 浙江大学物理系, 杭州 310027
  • 收稿日期:2005-09-21 修回日期:2005-12-01 发布日期:2006-04-10
  • 通讯作者: 陶向明 E-mail:mqtan@zju.edu.cn

A Density-functional Theory Study of Hydrogen Adsorption on Ti(0001) Surface

CHEN Wen-Bin;TAO Xiang-Ming;ZHAO Xin-Xin;TAN Ming-Qiu   

  1. Department of Physics, Zhejiang University, Hangzhou 310027, P. R. China
  • Received:2005-09-21 Revised:2005-12-01 Published:2006-04-10
  • Contact: TAO, Xiang-Ming E-mail:mqtan@zju.edu.cn

摘要: 用密度泛函理论研究了氢原子的污染对于Ti(0001)表面结构的影响. 通过PAW总能计算研究了p(1×1)、p(1×2)、3^1/2×3^1/2R30[deg]和p(2×2)等几种氢原子覆盖度下的吸附结构, 以及在上述结构下Ti(0001)面fcc格点和hcp格点的氢原子吸附. 结果表明, 在p(1×1)-H、p(1×2)-H、3^1/2×3^1/2R30[deg]-H和p(2×2)-H几种H原子覆盖度下, 以p(1×1)-H结构的单个氢原子吸附能为最大. 在p(1×1)-H吸附结构下, 由于氢原子吸附导致的Ti(0001)表面Ti原子层收缩的理论计算数值分别为-2.85%(hcp吸附)和-4.31%(fcc吸附), 因此实际上最有可能的情况是两种吸附方式都有一定的几率. 而实验中观察到的所谓“清洁”Ti(0001)表面实际上是有少量氢原子污染的表面. 不同覆盖度和氢分压下, 氢原子吸附的污染对Ti(0001)表面结构有极大的影响, 其表面的各种特性都会随覆盖度的不同而产生相应的变化.

关键词: Ti(0001)表面, 氢原子吸附, 表面污染

Abstract: The influence of hydrogen contamination on the atomic geometry of Ti(0001) surface have been studied by using the density-functional theory and the projector-augmented wave(PAW) method. Based on the optimized structural parameters of hcp Ti from the PAW total energy calculation, the surface relaxation, surface energy, and work function of clean Ti(0001) surface were calculated in the same way. The adsorption geometries and total energies of several coverages of hydrogen on Ti(0001) surface including p(1×1),p(1×2),3^1/2×3^1/2R30[deg], and p(2×2), were studied for the hcp and fcc site absorptions combined with the both sites occupation in p(1×1) structure. These results suggest that the Ti(0001) p(1×1)/H geometry has the largest energy gain among the above conformations, so under the condition of low coverage and low H2 pressure, the most possible conformation is p(1×1)-H adsorption. The shrink of Ti(0001) surface with H contamination was -3.7% from available experiments and this work yields -2.85% for hcp and -4.31% for fcc adsorption geometries, respectively. It is deduced that the most possible adsorption configuration for a hydrogen contaminated Ti(0001) surface is a mixture of hcp and fcc adsorptions. For a clean Ti(0001) surface the surface contraction is calculated to be near -7.0% while the experimental measurement predicted -4.9%. This observation implies that even for a “clean” Ti(0001) surface there is still about 13.6% surface area covered with hydrogen adsorption. These results reflect that the hydrogen contamination could affect the Ti(0001) surface structure dramatically. Furthermore the present study could yield a conclusion naturally that the shrink of the Ti(0001) surface will be reduced with the increase of H atom adsorption below 1.0 ML(monolayer).