Pressure increase of the electron-phonon interaction in superconducting hexagonal silicon

Using an ab initio pseudopotential approach, the pressure dependence of the electron-phonon interaction parameter $\lambda$ and the phonon frequencies for metallic hexagonal phases of silicon is calculated. With changing pressure $\lambda$ is found to go first through a minimum and then reach its maximum value near the phase transition from simple hexagonal (sh) to hexagonal close packed (hcp). At this point the superconducting transition temperature $T_c$ is expected to be above 10 K. In the hcp phase Si is predicted to be superconducting with $T_c$ in the same range as in the sh phase.