Prediction of new thermodynamically stable ZnN2O3 at high pressure.

Pressure has become a useful parameter to prepare novel functional materials. Considering the excellent performance of ZnO and Zn3N2 and the formation of strong Zn-O, Zn-N, and N-O bonds in the known compounds, we explored potential Zn-N-O ternary compounds with interesting properties. With the aid of first-principles swarm-intelligence search calculations, we identified a hitherto unknown ZnN2O3 ternary compound with a symmetry of P21. Its remarkable feature is that N pairs interconnect the distorted Zn-centered decahedrons, in which the Zn atom forms bonds with one N and six O atoms. The compression of ZnO + NO2 + N2 might be an easy way to synthesize ZnN2O3. Electronic property calculations disclose that ZnN2O3 is a wide band gap semiconductor with a gap value of 3.48 eV, which is larger than those of ZnO and Zn3N2. Moreover, the high-pressure phase diagram of Zn-N binary compounds was explored with a wide range of chemical compositions. Two metallic N-rich zinc nitrides (e.g., ZnN2 and ZnN4) are proposed, containing intriguing N2 dimers and zigzag N chains. ZnN2 exhibits superconducting properties, and becomes the first example of superconductor in zinc nitrides. Our current results unravel the unusual stoichiometry of Zn-N-O compounds and provide further insight into the diverse electronic properties of zinc nitrides under high pressure.