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) ų, 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 O^2- for N^3- 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.