Hello, I have a question about how non-magnetic impurities affect the transition temperature in type II superconductors. I know that the impurities introduce additional scattering and therefore act to reduce Tc, but is there a simple formula that would relate the effect on Tc due to particles of a particular size in relation to xi or lambda? Also, what about particle shape, as a sphere would cause scattering different from that of a long needle-like impurity? Most of the papers I have found present experimental results showing the decrease of Tc, but I haven't found any that cite where I could find a theoretical estimation for the reduction of Tc with a specific impurity. I have found some very lengthy and complex formulas in a few papers, but it was not clear to me how the size or shape would factor into these formulas. If you know a source or if you can guide me in the right direction, that would be helpful. Thank you!