Superconductivity and phonon softening. III. Relation between electron bands and phonons in Nb, Mo, and their alloys

Calculations are presented by χ₁(→Q) and χ₂(→Q,ω) for Nb, Mo, and alloys in the rigid-band model. The matrix elements are set to 1. The results for Nb agree with a previous calculation by Cooke, Davis, and Mostoller. An empirical linear relation is found between χ₁(→Q) and dχ₂(→Q,0)dω. This relation leads to a simple formula relating the superconducting coupling constant (λ) to the phonon frequencies. However, we are unable to evaluate the terms in this formula with sufficient accuracy to calculate λ.