First-principles band structure calculations were performed for the ternary alkaline-earth silicon nitride BaSi 7 N 1 0 using the density functional theory (DFT) within the pseudo-potential (PP) method. The calculations show that both the coordination number of nitrogen by silicon (N [ x ] ) as well as the way of sharing SiN 4 tetrahedra (corner vs. edge) influence the local electronic structure of these atoms. The top of the valence band is dominated by the 2p states of the N [ 2 ] atoms, while the N [ 3 ] 2p states are positioned lower in energy. It is also noted that edge-sharing N [ 3 ] atoms show N [ 2 ] character. The conduction band is determined by Ba 6s states. The compound is calculated to be a wide band gap semiconductor with an indirect energy gap of about 3.8 eV. The direct energy gap is predicted to be about 4.0 eV, in agreement with the experimental value of 4-4.5 eV.