On the Tc(x) dependence in the Ca(Al1−xGax)Si compound

The critical temperature dependence on Ga concentration in the inter-metallic pseudo-binary Ca(Al1−xGax)Si system is studied. Non-orthogonal tight binding calculations are reported which show that the main contribution to the density of states at the Fermi level (ρEF) comes from the Ca3d-orbitals. ρEF decreases almost linearly along the series. This does not explain the non-monotonic behavior of the critical temperature under Ga doping. On the contrary, our study suggests that upon gallium substitution the electron-phonon interaction potential is modified. This fact is claimed to be responsible for the parabolic-like Tc(x) dependence, which goes through a minimum around x ≈ 0.7.