First-principles calculation of the Coulomb pseudopotential mu* for the simple hexagonal phase of Si

Abstract

We calculate the Coulomb pseudopotential mu* for the simple hexagonal phase of Si at a pressure of 14 GPa using a full-dielectric-matrix approach within the local-density-functional approximation. With all of the screening effects such as the crystal potential, local-field, and exchange-correlation effects, the value of mu* is estimated to be 0.104. Considering only the crystal potential effect, mu* is found to be very close to that of a free-electron gas. The exchange-correlation effect on the electron dielectric response function decreases the dielectric screening, especially for large wave vectors, giving rise to an increase of mu*, while the local-field effect which results from directional bonds slightly reduces mu*.