物理化学学报 >> 2010, Vol. 26 >> Issue (01): 163-168.doi: 10.3866/PKU.WHXB20100133

量子化学及计算化学 上一篇    下一篇

含Pb铝合金表面的电化学溶解趋势

刘建才, 张新明, 陈明安, 唐建国, 刘胜胆   

  1. 中南大学材料科学与工程学院，长沙 410083
  • 收稿日期:2009-08-25 修回日期:2009-10-29 发布日期:2009-12-29
  • 通讯作者: 张新明 E-mail:xmzhang_cn@yahoo.cn

Electrochemical Dissolution Trends of Pb-Containing Al Alloy Surfaces

LIU Jian-Cai, ZHANG Xin-Ming, CHEN Ming-An, TANG Jian-Guo, LIU Sheng-Dan   

  1. School of Materials Science and Engineering, Central South University, Changsha 410083, P. R. China
  • Received:2009-08-25 Revised:2009-10-29 Published:2009-12-29
  • Contact: ZHANG Xin-Ming E-mail:xmzhang_cn@yahoo.cn

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摘要：

利用一个简单层状模型通过第一性原理的密度泛函理论研究了表面Pb含量变化对Al(100)表面Al原子的化学势和电化学溶解电势的影响规律. 计算结果表明, 当表面层Pb含量为1/9、1/4、1/2和3/4 ML(monolayer)时, 与纯铝相比, 表面Al原子的化学势分别升高了0.13、0.17、0.57和0.64 eV, 表面Al原子的溶解电极电势分别偏移了-0.04、-0.06、-0.19和-0.21 V. 溶解电势向负方向偏移, 表明含Pb的Al(100)表面的Al原子在更低的电势条件下就可以溶解了. 同时, 表面Pb含量不同会引起表面Al原子向内不同程度的弛豫, 导致表面Al的化学环境和表面结构发生变化, 进一步表明金属表面原子的化学势和溶解电极电势受原子周围的化学环境的影响. 表面Mulliken电荷布居分析证实, 随着表面Pb含量增加, Pb原子与Al原子之间的电荷交换作用增强, 使表面Al原子总的负电荷数增加, 导致表面电位下降,表面功函数也减小, 也促使Al表面更易于发生电化学腐蚀反应.

关键词: 第一性原理, 表面, 化学势, 溶解电极电势, Mulliken电荷布居

Abstract:

A simplified slab model was used to evaluate the effect of Pb content at the Al(100) surface on the chemical potentials and electrochemical dissolution potentials for pure Al and Al-Pb alloys using first-principles density functional theory calculations. Results indicated that the chemical potentials of the surface Al atoms, increased 0.13, 0.17, 0.57, and 0.64 eV, and their dissolution electrode potentials shifted -0.04, -0.06, -0.19, and -0.21 V with regards to pure Al when the content of Pb on the Al(100) surface was 1/9, 1/4, 1/2, and 3/4 monolayer coverages, respectively. The negative potential shift of the Pb-containing Al alloy indicates easier dissolution compared to the pure Al surfaces. The presence of Pb results in an inner relaxation of the Al surface atoms, and the surface structure as well as chemical environment changes. The chemical potential and the dissolution electrode potential are shown to be dependent on the chemical environment of the surface atoms. A Mulliken charge population analysis also indicate that at higher Pb content, the electron exchange between Pb and Al atoms increase, which results in a negatively charged aluminum surface and a reduced surface potential; the surface work function decreases, and this promotes the electrochemical corrosion of the aluminumsurface.

Key words: First-principles, Surface, Chemical potential, Dissolution electrode potential, Mulliken charge population