Abstract
This paper introduces key ingredients of the dielectric response of -alumina that go beyond an independent-particle (IP) treatment of the valence-electron excitations. The optical-response functions were calculated from first- principles both at the Bethe–Salpeter and the random-phase approximation (RPA) levels. Excitonic effects obtained within the Bethe–Salpeter framework were found essential for reproducing the low-energy part of the experimental spectra (below 15 eV) and the bound exciton in particular. For higher energies, local-field effects introduced through the RPA modified considerably the IP results and provided a satisfactory account of the reflectivity spectra and of the position and shape of the dominant bulk plasmon resonance in the electron energy-loss spectra.
3 More- Received 15 February 2011
DOI:https://doi.org/10.1103/PhysRevB.83.195129
©2011 American Physical Society