OPTICAL-PROPERTIES OF BETA-C3N4 AND ITS PRESSURE-DEPENDENCE

The electronic and the optical properties of beta-C3N4 are studied by means of first-principles local-density calculations. The structural properties obtained via total-energy calculations are in good agreement with the results of Liu and Cohen [Phys. Rev. B 41, 10 727 (1990)]. The frequency-dependent optical properties are calculated after an approximate self-energy correction scheme is applied to the energy spectrum. It is found that the band gap in beta-C3N4 increases linearly with pressure. The absorption spectrum shows two major peaks at 7.9 and 13.9 eV with a static dielectric constant of 3.2 predicted.