High-pressure stability and ambient metastability of marcasite-type rhodium pernitride

Abstract

High-pressure stability, ambient metastability, and high-pressure crystal chemistry of chemical bonds of marcasite-type RhN2 have been investigated using a laser-heated diamond-anvil cell up to a pressure of 70.6 GPa. High-pressure in-situ X-ray diffraction and Raman scattering measurements revealed that the marcasite-type RhN2 structure is stable up to 70.6 GPa and exhibited an order of axial compressibility of βc > βb > βa. This indicates that single bonded nitrogen dimer (N-N) plays an important role in the incompressibility of a- and b-axes than in that of the c-axis and stabilizes the marcasite-type structure at high-pressure. Field emission scanning electron microscopic analysis in combination with the energy dispersive X-ray spectroscopic measurements and the result of our previous study indicates that the marcasite-type RhN2 can be quenched to ambient pressure when the grain size is less than 100 nm. Our study together with other previous studies indicates that the ambient metastability of 4d platinum group pernitrides (RuN2, RhN2, and PdN2) decreases from ruthenium to palladium.

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

“…The deviation of this angle from the corresponding angle in the marcasite structure (90°) decreases with the pressure increase from 0.34(4)° at 39.3 GPa to 0.12(4)° at 51.7 GPa that is in agreement with the theoretical studies of Yu et al Arsenopyrite structure type is typical for dipnictides of group 9 metals MX 2 ( M = Co, Rh, Ir; X = P, As, Sb) . Our result disagree with works of Niwa et al,, who reported a marcasite‐type structure for RhN 2 on the basis of high‐pressure powder X‐ray diffraction. We should note, that it is rather challenging to recognize the peak splitting in a high‐pressure powder diffraction pattern (Figure j), as the high‐angle peaks are too weak to be clearly resolved.…”

“…The first indexing resulted in the orthorhombic lattice parameters ( a = 3.8540, b = 4.7106, c = 2.7068 Å) characteristic for marcasite type structure of rhodium pernitride RhN 2. , However, the detailed analysis of the diffraction pattern revealed several extra features that had to be explained. In particular, we observed that some of the reflections are split (Figure b–d).…”

High-pressure Na3(N2)4, Ca3(

“…Studies of the chemistry of nitrogen at high densities revealed the ubiquity of charged [N2] xdimers in binary nitrides. 12,13,[22][23][24][25][26][27][28][14][15][16][17][18][19][20][21] These were first discovered in the form of diazenides, [N2] 2-, in Sr8N4[N2]•(e -)2, Sr8N4[N2]2, SrN2, and BaN2, with N-N bond lengths of 1.22 Å, comparable to those in protonated diazene N2H2 (1.21-1.25 Å). [29][30][31] The family of compounds featuring charged dinitrogen species was later enlarged due to high-pressure synthesis of transition metals dinitrides (OsN2, IrN2, PtN2, TiN2) 20,23,24 displaying tetravalent [N2] 4anions with N-N bond distances of ~1.4 Å, similar to those in hydrazine N2H4 (1.47 Å).…”

A Study of the Electronic Structure and Elastic Properties for m-ZrO2 and -Bi2O3 Based on First-Principles Calculations under Ambient Pressure

“…At ambient conditions, the lattice constants of m-Zr02 and a-Bi2O3 are listed in table 1. The results are slightly larger than the experimental value [8,9], which are due to the systemic error in GGA. Electronic Structure.…”