Calculation of the superconducting transition temperature in niobium

We present calculations of the superconducting transition temperature T/sub c/, the electron-phonon coupling constant lambda, and the spectral function ..cap alpha../sup 2/f(..omega..), for niobium. Our calculations are based on an empirical-pseudopotential-method band structure. Phonon linewidths are also given for longitudinal and transverse branches along different directions. The necessary electron-phonon matrix elements are evaluated using only the rigid-ion approximation and applying Green's theorem to the nonlocal pseudopotential. The calculated value of T/sub c/ is 8.4 K and the calculated lambda is 1.02. The spectral function and linewidths are compared to experimental and previous theoretical results.