SRF2017 - List of Authors (Adlakha, I.)

Paper	Title	Page
THPB002	Role of Nitrogen on Hydride Nucleation in Pure Niobium by First Principles Calculations	741
	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
	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THPB002
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Paper

Title

Page

Role of Nitrogen on Hydride Nucleation in Pure Niobium by First Principles Calculations

741

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

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.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THPB002

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)