Hydrogen on the Fe(110) surface and near bulk bcc Fe vacancies - A comparative bonding study

SURFACE SCIENCE

卷:421

Article

Juan, A ; Hoffmann, R

关键词: electronic structure;    embrittlement;    Fe(110);    hydrogen;    molecular orbitals;    vacancy;   

DOI  :  10.1016/S0039-6028(98)00780-8

来源: Elsevier

【 摘 要 】

The bonding of H to Fe is analyzed using qualitative band structure calculations in the framework of extended Huckel tight-binding theory and the ASED-MO cluster method. The changes in the electronic structure of bcc Fe upon the introduction of H at a vacancy are addressed, and a comparison drawn with H adsorption at the Fe(110) surface. H in bulk Fe with vacancies prefers a tetrahedral site shifted toward the vacancy. The vacancies act as a strong trap for H. The Fe atoms are initially more strongly bonded to each other as a consequence of vacancy formation; their Fe-Fe bond strength is then diminished as the new Fe-H bond is formed. The effect of H is limited to its first Fe neighbor. An analysis of the orbital interactions reveals that the Fe-H bonding involves mainly the Fe 4s and H 1s orbitals with less participation of Fe 4p and 3d crystal orbitals. Relaxation of Fe atoms neighboring the vacancy is also addressed. A detailed atomistic mechanism for decohesion and H embrittlement is provided. (C) 1999 Elsevier Science B.V. All rights reserved.

【 授权许可】

Free