paper

High-pressure synthesis of ultraincompressible hard rhenium nitride pernitride Re $_{2}$ (N $_{2}$ )N $_{2}$ stable at ambient conditions

arXiv:1902.09249 · doi:10.1038/s41467-019-10995-3

Abstract

Here we report the synthesis of metallic, ultraincompressible (bulk modulus $K_{0}$ = 428(10) GPa) and very hard (nanoindentation hardness 36.7(8) GPa) rhenium (V) nitride pernitride Re $_{2}$ (N $_{2}$ )N $_{2}$ . While the empirical chemical formula of the compound, ReN $_{2}$ , is the same as for other known transition metals pernitrides, e.g. IrN $_{2}$ , PtN $_{2}$ , PdN $_{2}$ and OsN $_{2}$ , its crystal chemistry is unique. The known pernitrides of transition metals consist of a metal in the oxidation state +IV and pernitride anions N $_{2}^{4 -}$ . ReN $_{2}$ contains both pernitride N $_{2}^{4 -}$ and discrete N $^{3 -}$ anions, which explains its exceptional properties. Moreover, in the original experimental synthesis of Re $_{2}$ (N $_{2}$ )N $_{2}$ performed in a laser-heated diamond anvil cell via a direct reaction between rhenium and nitrogen at pressures from 40 to 90 GPa we observed that the material was recoverable at ambient conditions. Consequently, we developed a route to scale up its synthesis through a reaction between rhenium and ammonium azide, NH $_{4}$ N $_{3}$ , in a large-volume press at 33 GPa. Our work resulted not only in a discovery of a novel material with unusual crystal chemistry and a set of properties attractive for potential applications, but also demonstrated a feasibility of surmounting conceptions common in material sciences.

High-pressure synthesis of ultraincompressible hard rhenium nitride pernitride Re2​(N2​)N2​ stable at ambient conditions

Abstract

High-pressure synthesis of ultraincompressible hard rhenium nitride pernitride Re $_{2}$ (N $_{2}$ )N $_{2}$ stable at ambient conditions