Superconductivity in transition metal alloys: an alternative to the rigid band model. II

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Abstract
For part I see abstr. A79497 of 1973. In a recent paper an account has been given of the electronic heat capacities, gamma , of transition metal solid solutions in terms of an empirical model in which the different metals in the alloy are assumed to contribute individually to gamma . The model is applied to the superconductive transition temperature. It is demonstrated that a fair description of the experimental data available on superconductive transition metal solid solutions is obtained if in the alloy the metals are supposed to contribute individually to -(ln(Tc/ theta D)-1. Within a simple BCS formalism the additivity assumed for this quantity is equivalent to the additivity of densities of states and that of electronic heat capacities. In addition, both heat capacity and superconductivity of transition metal random alloys are reconsidered taking into account phonon enhancement and separate attractive and repulsive electron-electron interactions. It is concluded that the density of states at the Fermi level, N(0), shows maxima at Z approximately=3.3, 5.3, 7.3, 8.8 and 10. This result partly contradicts rigid band type conclusions.