The partial contribution of the sub-bands to λ f V₃Si

The band structure and the electron-phonon coupling constant are calculated for pi bands using a tight-binding parameter fit for V₃Si. Following this and previous calculations for the delta ₂ band and the sigma band hybridised with the delta ₁ band, an approximate relationship for the contribution to lambda from the various sub-bands of the 3 d band is developed. The relationship depends upon the individual width of the sub-band and its contribution to the density of states and shows that there is some compensation between N(0) (the electronic density of states at the Fermi level) and I² (the electron-phonon coupling constant). A narrow band gives rise to a large value of N(0) but a small value of I²; thus the product N(0)I² does not follow the behaviour of N(0).