First-principles calculation of superconductivity in pseudo-ternary silicides MGaSi (MÂ =Â Ca, Sr and Ba)

The linear response scheme and the full potential linear Muffin-tin-orbital (FP-LMTO) method are used to calculate the electronic structure, phonon spectrum and electron-phonon (EP) interaction for in-plane ordered MGaSi (M = Ca, Sr and Ba). Our calculated results clearly indicate that the ultrasoft mode exists in these three pseudo-ternary silicides, and it plays an important role in their superconductivity. The estimated values of Tc are in reasonable agreement with the experimental data.