Nb₃Sn offers the potential to significantly advance superconducting radio frequency (SRF) technology by improving the efficiency of accelerating cavities, but preserving the material's performance requires special attention to its microstructual properties. While the effects of point defects are well-understood, with superconducting properties that quickly degrade as the material deviates from its ideal stoichiometry, less is known about how performance is impacted by extended defects such as grain boundaries. Grain boundaries are defects that significantly disrupt the crystal structure and provide disorder on length scales comparable to the superconducting coherence length of Nb₃Sn. This study provides the first ab Initio investigation to predict the impact of grain boundaries on the superconducting performance of Nb₃Sn. In this study we identify an energetically favorable selection of grain boundary structures, examine the impact of grain boundaries on the material's electronic structure, explore the interactions between grain boundaries and point defects, and finally consider how all of these effects impact local superconducting properties.

Reference:

M. M. Kelley, N. S. Sitaraman, and T. A. Arias, “Ab Initio Theory of the Impact from Grain Boundaries and Substitutional Defects on Superconducting Nb₃Sn,” Superconductor Science & Technology, vol. 34, no. 1, p. 015015, Jan. 2021, doi: 10.1088/1361-6668/abc8ce.