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TY - CONF AU - Sitaraman, N. AU - Arias, T. AU - Carlson, J.M. AU - Cueva, P. AU - Kelley, M.M. AU - Liepe, M. AU - Muller, D.A. AU - Pack, A.R. AU - Porter, R.D. AU - Sun, Z. AU - Transtrum, M.K. ED - Michel, Peter ED - Arnold, André ED - Schaa, Volker RW TI - Ab Initio Calculations on the Growth and Superconducting Properties of Nb₃Sn J2 - Proc. of SRF2019, Dresden, Germany, 30 June-05 July 2019 CY - Dresden, Germany T2 - International Conference on RF Superconductivity T3 - 19 LA - english AB - In this work, we employ theoretical ab initio techniques to solve mysteries and gain new insights in Nb₃Sn SRF physics. We determine the temperature dependence of Nb₃Sn antisite defect formation energies, and discuss the implications of these results for defect segregation. We calculate the phonon spectral function for Nb₃Sn cells with different combinations of antisite defects and use these results to determine Tc as a function of stoichiometry. These results allow for the first-ever determination of Tc in the tin-rich regime, where experimental measurements are unavailable and which is critical to understanding the impact of tin-rich grain boundaries on superconducting cavity performance. Finally, we propose a theory for the growth mechanism of Nb₃Sn growth on a thick oxide, explaining the puzzling disappearing droplet behavior of Sn on Nb oxide and suggesting how in general an oxide layer reacts with Sn to produce a uniform Nb₃Sn layer. PB - JACoW Publishing CP - Geneva, Switzerland SP - 39 EP - 43 KW - site KW - cavity KW - niobium KW - SRF KW - electron DA - 2019/08 PY - 2019 SN - 978-3-95450-211-0 DO - doi:10.18429/JACoW-SRF2019-MOP010 UR - http://jacow.org/srf2019/papers/mop010.pdf ER -