Correlated Hartree-Fock energy bands for diamond

Abstract

The screened-exchange-plus—Coulomb-hole method has been used to add correlation to Hartree-Fock energy bands. These correlation corrections, or energy shifts, are state dependent due to the screened-exchange term. The Coulomb-hole term is constant throughout the zone in our diagonal approximation for the screening (dielectric) function. The energy shifts raise the occupied bands and lower the conduction bands with a resulting decrease in energy differences. The calculation has been done for diamond using linear combination of atomic orbitals Hartree-Fock bands and the Penn-model dielectric function. The energy shifts, which tend to flatten the bands, were computed at general points in the first zone. Values of 5.6 and 7.6 eV were obtained for the indirect and direct band gaps respectively, both of which are in close agreement with experiment. The diagonal part of the random-phase approximation was also used in the calculation and it was found to produce about two-thirds of the correlation obtained with the Penn model.