Velocity of sound and the BCS interaction parameter in five body-centred-cubic crystals

We first relate empirically the superconducting transition temperature, T_c, of the bcc d-band metals to the velocity of sound and the reduced Cauchy discrepancy c^* = (c₁₂−c₄₄)/(c₁₂+c₄₄). Then, to be definite, by restricting ourselves to the BCS formula for T_c, we relate the BCS electron–phonon interaction to the Debye temperature and the sound velocity. By contrast the six fcc metals with both filled (Cu, Ag, Au) and incomplete (Ni, Pd, Pt) d-shells, which are not superconducting at room temperature, do not display any such relationship and instead show trends in their elastic constants consistent with the bond-charge model.