Electronic structural properties of β-C3N4, β-Si3N4 and β-Ge3N4

Abstract

The electronic energy bands of a series of β-phases of carbon nitride, silicon nitride and germanium nitride have been calculated using a first-principle linear combination of muffin-tin orbital method with the atomic-sphere approximation (LMTO-ASA). The band gaps obtained for the three compounds are 4.18, 5.18 and 4.03 eV, respectively. For β-C3N4, the nitrogen 2p orbitals play an important role in the top of the valence band (VB) due to its non-bonding character. For β-Si3N4, the silicon 3d orbitals play an important role both in the VB and in the conduction band (CB). Its band gap is indirect which is in agreement with other calculated results. For β-Ge3N4, the germanium 4d empty orbitals play a role analogous to 3d of Si in β-Si3N4. Its 3d orbitals preserve the characteristics of atomic orbitals and give very little contributions to other VBs and the CB. This is the first theoretical study reported on the electronic structure of β-Ge3N4.