Effects of disorder on properties ofA15materials

We have calculated the effects of disorder on the density of states, Fermi velocity, and Drude plasma frequency for V and its $A15\mathrm{}$ compounds ${\mathrm{V}}_{3}X$, with $X=\mathrm{A}\mathrm{l},\mathrm{ }\mathrm{G}\mathrm{a},\mathrm{ }\mathrm{G}\mathrm{e},\mathrm{ }\mathrm{S}\mathrm{i},\mathrm{ }\mathrm{and}\mathrm{ }\mathrm{Sn}$, and for Nb and its $A15\mathrm{}$ compounds ${\mathrm{Nb}}_{3}X$, with $X=\mathrm{A}\mathrm{l},\mathrm{ }\mathrm{G}\mathrm{a},\mathrm{ }\mathrm{G}\mathrm{e},\mathrm{ }\mathrm{S}\mathrm{i},\mathrm{ }\mathrm{S}\mathrm{n},\mathrm{ }\mathrm{and}\mathrm{ }\mathrm{Sb}$ using the electron-lifetime model and the results of band-structure calculations. In most cases the density of states and the superconducting transition temperature $T_c$ are found to decrease with increasing disorder, in qualitative agreement with experiment. Exceptions are ${\mathrm{Nb}}_3$Sb and ${\mathrm{Nb}}_3$Si, for which we have found a small increase in $T_c$. We are also presenting calculations of the effects of disorder on the mean free path, BCS coherence length, London penetration depth, Ginzburg-Landau $\kappa$, and the temperature dependence of the upper critical field for the above materials. Comparison with the existing experimental data is made.