Random-phase-approximation dielectric function for diamond, with local field effects included

Abstract

The diagonal part of the static wave-vector-dependent random-phase-approximation (RPA) dielectric function was computed for diamond using both Hartree-Fock energies and screened exchange plus Coulomb hole correlated energies, and in both cases, the diagonal RPA was found to be smaller than the experimental value as represented by the Penn model. Next the full RPA dielectric matrix was calculated using seven sets of reciprocal-lattice vectors. The matrix was then inverted and the reciprocal of the first diagonal term of the inverse was taken, yielding the diagonal RPA with local-field effects included. Special techniques were employed to handle the singularities that appear in the dielectric matrix when the wave vector goes to zero. The diagonal RPA with local-field effects included was found to be smaller, and thus farther from experiment, than the diagonal RPA that was calculated initially. Hartree energy bands were also used to compute the diagonal RPA, and the result was a significant improvement over the previous calculations and quite a bit closer to experiment.