High-pressure synthesis of ultraincompressible hard rhenium nitride pernitride Re2(N2)(N)2 stable at ambient conditions

Abstract

High-pressure synthesis in diamond anvil cells can yield unique compounds with advanced properties, but often they are either unrecoverable at ambient conditions or produced in quantity insufficient for properties characterization. Here we report the synthesis of metallic, ultraincompressible ( K 0 = 428(10) GPa), and very hard (nanoindentation hardness 36.7(8) GPa) rhenium nitride pernitride Re 2 (N 2 )(N) 2 . Unlike known transition metals pernitrides Re 2 (N 2 )(N) 2 contains both pernitride N 2 4− and discrete N 3− anions, which explains its exceptional properties. Re 2 (N 2 )(N) 2 can be obtained via a reaction between rhenium and nitrogen in a diamond anvil cell at pressures from 40 to 90 GPa and is recoverable at ambient conditions. We develop 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. Although metallic bonding is typically seen incompatible with intrinsic hardness, Re 2 (N 2 )(N) 2 turned to be at a threshold for superhard materials.

Organic acids under pressure: elastic properties, negative mechanical phenomena and pressure induced phase transitions in the lactic, maleic, succinic and citric acids

“…The pressure induced phase transitions and structural transformations may be advantageously used, for example, in high-pressure synthesis, mechanochemistry and nanotechnology. 35,[119][120][121][122][123][124][125][126][127][128][129][130][131][132][133] Mechanically responsible organic crystals showing macroscopic motion as a response to pressure or deformation are very interesting due to their potential applications in nanotechnology as organic actuators. 98,[130][131][132][133] The mechanical response of molecular crystals, polymers and organic materials related to living organism physiology is of direct and enormous interest for the human being.…”

Synthesis of Arsenopyrite‐Type Rhodium Pernitride RhN2 from a Single‐Source Azide Precursor

“…Dinitrides of transition metals attract much attention due to their exceptional mechanical properties such as low compressibility and high hardness (the bulk modulus K 0 = 428 GPa for IrN 2 and ReN 2 ) , . Synthesis of such dinitrides requires very high pressure above 40–50 GPa and a simple synthetic route, which was actively exploited in the recent years, is a direct reaction between a metal and nitrogen in a laser‐heated diamond anvil cell (LHDAC).…”

Novel Rhenium Carbides at 200 GPa

“…Two carbides, Re 2 C and ReC, are isostructural to Re 2 N and ReN. They are built up of CRe 6 or NRe 6 trigonal prisms, and even Re–C and Re–N interatomic distances at the same pressures are very similar , . Contrary, the structures of ReC 2 and ReN 2 have nothing in common and there are no signs of formation of rhenium polycarbides with more than two carbon atoms per a formula unit at least up to 180(7) GPa and 3000 ± 300 K, unlike to the rhenium‐nitrogen system .…”

“…Chemical compounds of 5d transition metals and carbon or other first‐row elements, as B and N, often possess interesting properties attributed to strong covalent bonding . Many of carbides, borides, and nitrides reveal very high melting points (for example, over 3500 K for ZrC, NbC, HfC, TaC), large bulk moduli (K 0 > 390 GPa for Re 2 C, Re 2 N, ReN 2 , IrN 2 , OsB, Os 2 B 3 , OsB 2 ), and very high hardness (H v > 35 GPa for ReN 2 , WB 4 ). Transition‐metal carbides belong to a large group of industrially important materials.…”