Structures of lithium nitride (R-Li 3 N) and ternary nitridometalates Li 3-x-y M x N (M ) Ni, Cu) have been refined from time-of-flight powder neutron diffraction data using the Rietveld method. The parent binary nitride was synthesized by reaction of lithium metal with nitrogen using liquid sodium as a solvent. The ternary nitrides were prepared by reaction of Li 3 N with the respective transition metals under nitrogen. Refined data confirm the hexagonal structure previously reported by single-crystal X-ray diffraction for lithium nitride (P6/mmm, a ) 3.6576(1) Å, c ) 3.8735(1) Å, Z ) 1) and show that the R-Li 3 N phase contains close to 3% Li vacancies at room temperature. The substituted nitridometalates, Li 1.36 Ni 0.79 N and Li 2.21 Cu 0.40 N, both form structures analogous to R-Li 3 N (P6/mmm, a ) 3.7697(1) Å, c ) 3.5270-(1) Å and a ) 3.6791(1) Å, c ) 3.7725(1) Å, respectively) in which the transition metal is disordered with Li between [Li 2-y N] planes and Li vacancies are disordered within these planes. The nickel and copper nitrides contain 43% (y ) 0.85) and 16% (y ) 0.32) Li vacancies, respectively, within the [Li 2 N] planes and consequently contain transition metals predominantly in the +2 oxidation state.

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The structure, Li+ diffusion dynamics, and magnetic properties of the layered nitridonickelate(II), LiNiN, have been investigated by powder X-ray diffraction, 7Li solid-state NMR, and SQUID magnetometry and compared and contrasted with those of the Li+ fast ion conductor, Li3N. The replacement of Li+ by Ni2+ with concomitant generation of Li+ vacancies has profound effects on ionic diffusion and electronic properties. The nitridonickelate, akin to its binary parent, displays rapid Li+ ion diffusion but, by contrast, the diffusion process is confined only to the Li-N planes. Further, replacement of Li by Ni leads to a transition from semiconducting to metallic behavior, likely mediated through the creation of infinite, 1D Ni-N chains of increased covalency.