| Title |
Role of Nitrogen on Hydride Nucleation in Pure Niobium by First Principles Calculations |
| Authors |
- P. Garg, I. Adlakha, K.N. Solanki
Arizona State University, Tempe, USA
- S. Balachandran, P.J. Lee
NHMFL, Tallahassee, Florida, USA
- T.R. Bieler
Michigan State University, East Lansing, Michigan, USA
|
| Abstract |
It is known that formation and growth of Nb hydride degrades superconducting radio frequency (SRF) properties of Nb cavities and the treatments that reduce H concentration improve quality factor. Recently it is has also been shown that addition of N through doping or infusion improves the quality factor. Thus, we probe role of N addition in Nb on hydride precipitation and stability through first principles calculations & compared with coupon samples. In presence of N, energetic preference for H to occupy interstitial sites in the vicinity of N is reduced. Furthermore, presence of N forces H to occupy interstitial octahedral site instead of a tetrahedral site. The thermodynamic stability of hydride is decreased in the presence of N in Nb.The quantum insights using charge transfer and density of states show a strong tendency of N to accumulate charge, thereby decreasing the bond strength of neighboring Nb and H atoms. These atomic scale results explain the lesser tendency of surface hydride formation in SRF Nb cavities in presence of N. These results are consistent with metallographic examination of N-treated Nb coupons, which show suppressed hydride formation near N-treated surface.
|
| Paper |
download THPB002.PDF [1.233 MB / 5 pages] |
| Export |
download ※ BibTeX
※ LaTeX
※ Text/Word
※ RIS
※ EndNote |
| Conference |
SRF2017, Lanzhou, China |
| Series |
International Conference on RF Superconductivity (18th) |
| Proceedings |
Link to full SRF2017 Proccedings |
| Session |
Poster Session |
| Date |
20-Jul-17 14:00–17:00 |
| Main Classification |
Fundamental SRF R&D |
| Sub Classification |
Bulk Niobium |
| Keywords |
ion, niobium, site, cavity, electron |
| Publisher |
JACoW, Geneva, Switzerland |
| Editors |
Volker RW Schaa (GSI, Darmstadt, Germany); Yuan He (IMP, Lanzhou, China); Lu Li (IMP, Lanzhou, China); Ning Zhao (IHEP, Beijing, China) |
| ISBN |
978-3-95450-191-5 |
| Published |
January 2018 |
| Copyright |
|
