Crystal Chemistry and Electronic Structure of the Metallic Ternary Nitride, SrTiN2

The crystal chemistry and electronic structure of the layered nitride SrTiN2 have been studied by powder neutron diffraction (PND) and density functional methods, respectively. PND investigations at room temperature, 80 K, and 2 K show that the tetragonal KCoO2 structure (space group P4/nmm (No. 129), a = 3.8823(1) Å, c = 7.7008(1) Å, V = 116.068(1) Å3, Z = 2 at 298 K) is retained across the temperature range and confirm the structural model from previous room-temperature powder X-ray diffraction (PXD) studies. Furthermore, and importantly, PND data demonstrate that neither nitrogen nonstoichiometry nor substitution of O2- for N3- within the anion sublattice is a plausible mechanism for hole generation. Density functional calculations show that strong covalent bonding occurs within the TiN2 layers and that Sr−N interactions are pivotal in determining the band structure at the Fermi level. Calculations predict metallic and paramagnetic behavior for SrTiN2. These findings are confirmed by experimental measurements.