期刊
NUCLEAR FUSION
卷 59, 期 10, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1741-4326/ab33e7
关键词
tungsten; hydrogen; surface; DFT; activation barriers; coverage; desorption
资金
- Euratom research and training program 2014-2018 [633053]
- Euratom research and training program 2019-2020 [633053]
- Excellence Initiative of Aix-Marseille University-A*MIDEX, a French Investissements d'Avenir programme
Herein we investigate absorption and desorption of hydrogen in the sub-surface of tungsten via density functional theory. Both the near-surface diffusion and recombination of a bulk hydrogen atom with a hydrogen atom adsorbed upon the W(110) and W(100) surfaces are investigated at various surface adsorption coverage ratios. This study intends to model the desorption processes occurring during thermal-desorption spectroscopy experiments and the absorption of hydrogen during gaseous or low energy atomic exposure. Since the diffusion and recombination processes are expected to change as the hydrogen coverage of the surface varies, different coverage ratios were investigated on both surfaces. We found that at a saturation coverage of hydrogen on both surfaces, the activation barriers for the recombination of molecular hydrogen are below 0.8 eV. On the contrary, below saturation, the activation barriers for recombination rise to 1.35 eV and 1.51 eV depending on the coverage and on the orientation of the surface. Regarding the absorption of atomic hydrogen from the surface into the bulk, the activation barrier raises from less than 1.0 eV at saturation to around 1.7 eV below saturation on both surfaces. These results indicate that surface mechanisms certainly play a significant role in the kinetics of desorption of hydrogen from tungsten; it is also expected that surface mechanisms affect the total amount on hydrogen absorbed in tungsten during implantation.
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