期刊
APPLIED SURFACE SCIENCE
卷 465, 期 -, 页码 833-845出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.apsusc.2018.09.220
关键词
Density functional theory (DFT) calculations; Fe(100); Vacancy defects; Dissociation energy barrier; Diffusion path
类别
资金
- National Natural Science Foundation of China [51671215, 51805292, 21503273]
- National Postdoctoral Program for Innovative Talents [BX201700132]
Vacancy defects on an iron surface have a great influence on the occurrence of hydrogen embrittlement. The adsorption/dissociation mechanism of H2S and the diffusion behavior of H atoms were calculated by first-principles spin-polarization density functional theory (DFT) on defect-free and vacancy-defective Fe(100) surfaces. The results show that the maximum dissociation energy barriers of H2S on the Fe(100) surface of defect-free and first-layer vacancy-defective Fe are 0.35 and 0.17 eV, respectively, indicating that the reactivity of the vacancy-defective Fe(100) surface is moderately increased. The existence of vacancy defects changes the preferential H atom diffusion entrance to the subsurface and shortens the diffusion path. For H diffusion in bulk Fe(100), it is found that H atoms diffuse via a tortuous path from one tetrahedral-site to a neighboring tetrahedral-site rather than diffusing through a linear trajectory. Moreover, the previously suggested path via the octahedral site is excluded due to its higher barrier and the rank of the saddle point. Diffusion barriers computed for H atom penetration from the surface into the inner-layers are approximately 0.54 eV (except for second-layer vacancy defects), which are all greater than the activation energy for dissociation of H2S on the Fe(100) surfaces. This suggests that H diffusion is more probable than H2S dissociation as the rate-limiting step for hydrogen permeation into the bulk Fe(100).
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