UC Berkeley

The effect of disorder on the normal state resistivity and the superconducting properties of Nb3Sn Sn is explored in a combination of ab initio calculations and microscopic theory. The crystal symmetry is calculated to be preferentially tetragonal at a normal state resistivity below 27.0 ±1.4 μcm, and preferentially cubic above this value, which is shown to be consistent with the experimentally observed transition point. The phonon density of states, the Eliashberg spectrum a2 (w)F (w), the electronphonon coupling constant, the characteristic frequency, the critical temperature Tc, and the upper critical magnetic field at 0 K Hc2 (0) are calculated over a large normal state resistivity range and shown to be consistent with experimental observations. The high degree of consistency between the calculation results and experimental observations is a strong indication that the calculation approach utilized here, a combination of ab initio calculations and microscopic theory, is a useful tool for understanding the superconducting and normal state properties of Nb3Sn.