Electronic structure of magnesium nitride-fluorides from first-principles calculations

Electronic structure and stability have been determined from first-principles calculations for the magnesium nitride-fluorides Mg₂NF and Mg₃NF₃, as well as for the binaries MgF₂ and Mg₃N₂. These calculations show that the compounds are ionic to a first approximation. In the nitride-fluorides the valence bands are mainly determined by the N 2p states while the F 2p states are well separated from the N 2p bands and lie 3.5-5.1 eV below the Fermi level. The bottom of the conduction bands is determined by the empty 3s states of the anions. The energy gap decreases steadily with increasing nitrogen content.