A Map of the Inorganic Ternary Metal Nitrides Wenhao Sun1, Christopher Bartel2, Elisabetta Arca3, Sage Bauers3, Bethany Matthews4, Bernardo Orvañanos1, Janet Tate4, Bor-Rong Chen,5 Laura Schelhas,5 Michael F. Toney,5 William Tumas3, Andriy Zakutayev3, Stephan Lany3, Aaron Holder3, Gerbrand Ceder1 Nitrides are an exciting class of solid-state compounds, How does chemistry drive the stability with unique structures and compelling properties for next-generation functional materials. of the ternary metal nitrides? Unfortunately, nitrides are rare in nature and difficult Stable ternary nitrides lie on the N to synthesize. There are only ~300 unique ternary convex hull, shown on the right. 2 The energy of a ternary nitride can Thermochemical metal nitrides in the ICSD, in contrast to over 4,000 be expressed relative to the hull as competition Depth of A-N w/ binaries binary hull ternary metal oxides. ΔE = E – E – E Hull A-B-N A-N B-N A We employ a suite of high-throughput computational We explain ternary stability from materials discovery tools to broadly survey stability 1.) stability of the competing B relationships across the inorganic ternary metal binaries, and 2.) quantum chemical Electronic Interaction solid-state bonding in the ternary. of A and B in ternary nitrides. By clustering the ternary nitrides into chemical families Thermochemical competition with binary nitrides ‘Depth of the Binary Hull’ is the energy with distinct stability and metastability, we produce a Li of lowest-energy binary nitride in a Ca map that visualizes both promising and risky Sr Me-N space, and serves as a proxy for Ba compositions for further exploratory synthesis. the strength of the solid-state metal- Zn Mg Na nitrogen bond Mo Zr C K Co Mn Cs We reveal the fascinating interplay between chemistry, When plotting stable ternary spaces vs. Hf Ta Nb W Re Ni Rb depth of binary hull, a ‘volcano’ plot Ti Al V Cr Fe Ru Si Ge Os nitride composition, and solid-state bonding in Sc Y Sb Pt B Ga In Ir Se emerges, where ternaries are unstable Cu Bi Cd Te Stable Ternary Spaces Ternary Stable Sn governing the stability of ternary nitrides. against binaries with deep hulls, or do Rh Pd S not form at all if Me-N bonding is weak Pb Ag Au Portion of in the first place. Ternary M -M -N Spaces Previously Known Newly Predicted 1 2 map Depth of the Binary Hull (eV/atom) Stable Ternary Systems (Blue) 189 92 281 (26%) Alkali and Alkaline Earth form stable M-N bonds are very strong Intermediate M-N bonds are weak - Stable Alkali-Metal-Nitride Systems 124 76 200 ternaries more readily than elements Binaries are too stable, Good to form Nitrides unlikely to - Stable Metal-Metal-Nitride Systems 65 16 81 with similar hull depth. Ternaries likely to decompose ternaries nitrides with form in this chemistry Metastable vs. Stable Binaries, ΔHf < 0 (Green) 98 322 420 (44%) Metastable vs. Elements, ΔH > 0 (Red) 20 241 261 (27%) f Electronic Interaction of A and B in ternary Ternary AxByNz Phases Previously Known Newly Predicted Total Number Stable Ternary Phases 213 203 416 We conduct a large-scale data-mining Metastable, ΔEHull < 70 meV/atom 39 36 75 Ionicity Ionicity New Stable Experimentally Stabilizable analysis of chemistry, nitride composition, Metastable, ΔEHull < 200 meV/atom 85 175 260 Metastable vs. Metastable vs. Alkali-Metal-N Metal-Metal-N Ternary Space Known in ICSD ΔμN2 < 1 eV/N Stable and solid-state bonding in governing the Metastable: Stabilizable ΔμN < +1 eV/N 3 92 95 Binaries Elements stability of 353 ternary metal nitrides. N-Rich N-Rich 243 compounds 19 compounds CONSTRUCTION OF THE MAP SYNTHESIS OF NEW NITRIDES We use reactive sputtering to Data-mined ionic substitution suggests new synthesize 10+ new Zn- and Multi-Feature Hierarchical Agglomeration reveals M-M N-Poor M-N M-M N-Poor M-N ternary nitride structures based on rational ionic underlying relationships and chemical families Mg- based ternary nitrides Metallicity 56 compounds Covalency Metallicity 35 compounds Covalency Solid-State Bonding Molecular substitutions on known phases Sr6Ga5N across the ternary metal nitrides chemical space Mg-based ternary nitrides tend to Orbital Theory MgTa N 2 3 Na IrN crystallize in rocksalt-derived Sr4In2N 3 2 Oxidized Oxidized structures, whereas Zn-based KPtN ternary nitrides form in a Wurtzite- Ca2InN derived structure Metallicity: COHP-computed A-A, B-B, A-B and bonds Covalency: COHP-computed A-N, B-N, and N-N bonds New ternary nitrides are all Reduced Ionicity: Ratio of Net Atomic Charges (NAC) over the Reduced semiconductors with Egap ~ 1-2 eV Summed Bond Order (SBO) obtained from the Density Derived Electrostatic and Chemical (DDEC) Reduced Oxidized Reduced Oxidized ICSD Predicted Formation energy Formation energy Metastable stable compounds of all compounds / Unstable By changing the Zn:Mo ratio in Zn- Train DMSP Cross-validated by “predicting” We extend the 300 Mo-N ternaries, we can modulate algorithm on known nitrides. ~80% chance of nitrides to 6000 Clustering on individual features gives cluster maps with limited scope. Inductive effect, electropositive metal A known Pnictides recovery. ternary nitrides the molybdenum oxidation state 4+ 6+ donates electron density to B-N covalent We develop a multi-feature distance metric that captures high-level from Mo to Mo , turning We evaluate phase stability of DMSP-predicted structures using bond, oxidizing the more electronegative stability trends and local-scale chemical relationships metallic ZnMoN2 into a wide- tools within the Pymatgen and Materials Project infrastructure metal, which can lead to nitrogen-rich bandgap Zn3MoN4 semiconductor Multi-factor Clustering: Data-Type nitrides. DMSP offers an efficient way to probe both nitride structures and - Formation Energies Continuous This redox-mediated behavior stoichiometries over a broad compositional space. - Stable/Metastable/Unstable Nominal suggests a new class of Reductive effect, nitrogen oxidation or - Chemical group Ordinal IIx-TM-N semiconductors, with nitrogen deficiency provides electrons to DMSP may not predict the ground-state structure if a prototype tunable optoelectronic properties. Me-Me bonds, reducing the metals and structure does not exist. However, identification of a ternary with Gower Metric: Linear combination of distance metrics i “Redox Mediated Stability in Zinc Molybdenum Nitrides increasing metallicity. ΔHf < 0 in an otherwise empty space highlights that space for G= W d with user-assigned weights Elisabetta Arca et al., JACS, (2018) M1− M 2 i M 1 -M 2 further investigations of ground-state structures. i.