Crystal and Electronic Structure of U₇Te₁₂-Type Tungsten Nitride Synthesized under High Pressure

Abstract

Tungsten nitride continues to drive fundamental interests because of its potential as a functional compound, which combines features such as high hardness together with thermal, chemical, and wear resistance. Here, we report a novel tungsten nitride phase synthesized from MoC-type WN0.6 and molecular nitrogen after laser irradiation at P = 70 GPa in a diamond anvil cell. This novel phase is quenchable at ambient pressure and determined to be U7Te12-type tungsten nitride and crystallizes in the hexagonal space group (P ) having lattice parameters of a = 8.2398(3) Å, c = 2.94948(14) Å, and V = 173.423(13) Å3. Tungsten atoms are coordinated to eight and nine nitrogen atoms, higher than previously reported tungsten nitrides. The bulk modulus is determined to be K 0 = 312 (5) GPa (K 0 ′ = 4.0 fixed), and DFT calculations predict that U7Te12-type W7N12 has a metallic nature.

Synthesis, Crystal Structures, Mechanical Properties, and Formation Mechanisms of Cubic Tungsten Nitrides

“…High-pressure ( P ) and high-temperature ( T ) synthesis is an effective approach for preparing TM nitrides, , especially for the nitrogen-rich nitrides. A recent surge of studies along this line has led to the discovery of many exotic nitrides as exemplified by r - and h -W 2 N 3 , cP7-W 3 N 4 , , tungsten hexanitride (WN 6 ), and MoC- and U 7 Te 12 -type tungsten nitrides , in the W–N family and more. ,− …”

“…High-pressure (P) and high-temperature (T) synthesis is an effective approach for preparing TM nitrides, 2,19 especially for the nitrogen-rich nitrides. A recent surge of studies along this line has led to the discovery of many exotic nitrides as exemplified by r-and h-W 2 N 3 , cP7-W 3 N 4 , 9,20 tungsten hexanitride (WN 6 ), 21 and MoC-and U 7 Te 12 -type tungsten nitrides 22,23 in the W−N family and more. 5,24−38 Here, we perform high-P synthesis of high-quality cubic tungsten nitrides using our recently formulated reaction route, 5,9,24,39 leading to definitively solved crystal structures involving the disordered and ordered N vacancies, by the stateof-the-art neutron and X-ray diffraction (XRD) experiments.…”

Bulk and film synthesis pathways to ternary magnesium tungsten nitrides

“…Furthermore, the W-N binary system is complex, with 13 unique structures reported in the Inorganic Crystal Structure Database (ICSD) ranging in composition from W 2 N to WN 2 . [40][41][42][43][44] Given this complexity and ambiguity, we simply refer to these Mg-poor phases as WN x . This difference may stem from the elevated nitrogen chemical potential present in combinatorial depositions but absent during annealing, which may affect how much nitrogen is present in the film.…”

High-pressure synthesis and crystal structures of molybdenum nitride Mo3N5 with anisotropic compressibility by a nitrogen dimer

“…These high-pressure phases have not only been discovered experimentally but have also been synthesized through prediction by theoretical calculations, for example, U 2 S 3 -type Nb 2 N 3 14,21 and CuAl 2 -type VN 2 . 11,22 Recently, however, we have synthesized U 7 Te 12 -type W 7 N 12 16 that was not predicted by theoretical calculations, indicating the importance of experimental structural exploration and the determination of the high-pressure phase.…”

“…On the other hand, 4d and 5d early transition-metal nitrides, unlike late and 3d early transitionmetal dinitrides, have non-simple compositions, e.g., Zr 3 N 4 and Hf 3 N 4 for Th 3 P 4 -type, 13 Nb 2 N 3 14 and Ta 2 N 3 15 for U 2 S 3type, and W 7 N 12 for U 7 Te 12 -type. 16 Although these nitrides are not pernitrides due to the non-existence of N-N dimers, they are dense nitrides containing metal sites coordinated to seven or more nitrogen atoms. Moreover, Bykov et al synthesized rhenium nitride pernitride ReN 2 , formally Re 2 (N 2 )(N) 2 , containing both the N-N dimer and nitride ions.…”