<i>Ab Initio</i> Study of Impurity and Defect Scattering of Electrons in Nb and Nb₃Sn*

This talk will present ab initio density functional theory results on the effect of defects and impurities in Nb and Nb₃Sn on electron mean free path at cryogenic temperatures. The mean free path is a key quantity of interest for scientists studying the properties of superconducting radiofrequency (SRF) cavities used in particle accelerators. Using a Wannier-function based approach, we calculate electron velocities and scattering lifetimes for dense samples of states near the complex Fermi surfaces of these materials. We compare the resulting mean free path estimates to experimental measurements, and present insights into the relative importance of different impurities and defects. We discuss other potential applications of the Wannier-function method to the study of impurites and defects, such as the calculation of inelastic scattering amplitudes.