Calculated Nb superconducting transition temperature under hydrostatic pressure

A full-potential linear muffin-tin orbital method (FP-LMTO) based linear-re sponse approach is used to calculate the electron-phonon coupling in Nb und er hydrostatic pressure. The superconducting transition temperature T-c is calculated using the Eliashberg equation. The calculated T-c agrees nicely with the experimental result at ambient pressure, but the agreement is only fair at high pressures. The T-c measured anomaly at 60-70 GPa is understoo d in terms of the 2.5 order Lifshitz transition and its origin is traced ba ck to the qualitative changes in the Fermi surface topology.