Synthesis and Stability of High-Energy-Density Niobium Nitrides under High-Pressure Conditions.

High-energy-density materials (HEDMs) are crucial in various applications, from energy storage to defense technologies. Transition metal polynitrides are promising candidates for HEDMs. Using single-crystal synchrotron X-ray diffraction, we investigated the crystal structures of niobium nitride, specifically NbN and NbN, under high-pressure conditions of up to 86 GPa.

Synthesis of LaCN, TbCN, CeCN, and TbCN Polycarbonitrides at Megabar Pressures.

Inorganic ternary metal-C-N compounds with covalently bonded C-N anions encompass important classes of solids such as cyanides and carbodiimides, well known at ambient conditions and composed of [CN] and [CN] anions, as well as the high-pressure formed guanidinates featuring [CN] anion. At still higher pressures, carbon is expected to be 4-fold coordinated by nitrogen atoms, but hitherto, such CN-built anions are missing. In this study, four polycarbonitride compounds (LaCN, TbCN, CeCN, and TbCN) are synthesized in laser-heated diamond anvil cells at pressures between 90 and 111 GPa.

Extending carbon chemistry at high-pressure by synthesis of CaC and CaC with deprotonated polyacene- and para-poly(indenoindene)-like nanoribbons.

Metal carbides are known to contain small carbon units similar to those found in the molecules of methane, acetylene, and allene. However, for numerous binary systems ab initio calculations predict the formation of unusual metal carbides with exotic polycarbon units, [C] rings, and graphitic carbon sheets at high pressure (HP). Here we report the synthesis and structural characterization of a HP-CaC polymorph and a CaC compound featuring deprotonated polyacene-like and para-poly(indenoindene)-like nanoribbons, respectively.

High-pressure Synthesis of Cobalt Polynitrides: Unveiling Intriguing Crystal Structures and Nitridation Behavior.

In this study, we conduct extensive high-pressure experiments to investigate phase stability in the cobalt-nitrogen system. Through a combination of synthesis in a laser-heated diamond anvil cell, first-principles calculations, Raman spectroscopy, and single-crystal X-ray diffraction, we establish the stability fields of known high-pressure phases, hexagonal NiAs-type CoN, and marcasite-type CoN within the pressure range of 50-90 GPa. We synthesize and characterize previously unknown nitrides, CoN, Pnma-CoN and two polynitrides, CoN and CoN, within the pressure range of 90-120 GPa.

Diverse high-pressure chemistry in Y-NHBH and Y-paraffin oil systems.

The yttrium-hydrogen system has gained attention because of near-ambient temperature superconductivity reports in yttrium hydrides at high pressures. We conducted a study using synchrotron single-crystal x-ray diffraction (SCXRD) at 87 to 171 GPa, resulting in the discovery of known (two YH phases) and five previously unknown yttrium hydrides. These were synthesized in diamond anvil cells by laser heating yttrium with hydrogen-rich precursors-ammonia borane or paraffin oil.

Thermal Equation of State of Cubic Silicon Carbide at High Pressures.

We have performed in situ X-ray diffraction measurements of cubic silicon carbide (SiC) with a zinc-blende crystal structure (B3) at high pressures and temperatures using multi-anvil apparatus. The ambient volume inferred from the compression curves is smaller than that of the starting material. Using the 3-order Birch-Murnaghan equation of state and the Mie-Grüneisen-Debye model, we have determined the thermoelastic parameters of the B3-SiC to be K=228±3 GPa, K',=4.

High-pressure reactions between the pnictogens: the rediscovery of BiN.

We explore chemical reactions within pnictogens with an example of bismuth and nitrogen under extreme conditions. Understanding chemical reactions between Bi and N, elements representing the first and the last stable elements of the nitrogen group, and the physical properties of their compounds under ambient and high pressure is far from being complete. Here, we report the high-pressure high-temperature synthesis of orthorhombic BiN (S.

Synthesis of Ultra-Incompressible and Recoverable Carbon Nitrides Featuring CN Tetrahedra.

Carbon nitrides featuring three-dimensional frameworks of CN tetrahedra are one of the great aspirations of materials science, expected to have a hardness greater than or comparable to diamond. After more than three decades of efforts to synthesize them, no unambiguous evidence of their existence has been delivered. Here, the high-pressure high-temperature synthesis of three carbon-nitrogen compounds, tI14-C N , hP126-C N , and tI24-CN , in laser-heated diamond anvil cells, is reported.

Title: Structure determination of ζ-N from single-crystal X-ray diffraction and theoretical suggestion for the formation of amorphous nitrogen.

The allotropy of solid molecular nitrogen is the consequence of a complex interplay between fundamental intermolecular as well as intramolecular interactions. Understanding the underlying physical mechanisms hinges on knowledge of the crystal structures of these molecular phases. That is especially true for ζ-N, key to shed light on nitrogen's polymerization.

Stabilization of Guanidinate Anions [CN ] in Calcite-Type SbCN.

The stabilization of nitrogen-rich phases presents a significant chemical challenge due to the inherent stability of the dinitrogen molecule. This stabilization can be achieved by utilizing strong covalent bonds in complex anions with carbon, such as cyanide CN and NCN carbodiimide, while more nitrogen-rich carbonitrides are hitherto unknown. Following a rational chemical design approach, we synthesized antimony guanidinate SbCN at pressures of 32-38 GPa using various synthetic routes in laser-heated diamond anvil cells.

Stabilization Of The CN Anion In Recoverable High-pressure Ln O (CN ) (Ln=La, Eu, Gd, Tb, Ho, Yb) Oxoguanidinates.

A series of isostructural Ln O (CN ) (Ln=La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates was synthesized under high-pressure (25-54 GPa) high-temperature (2000-3000 K) conditions in laser-heated diamond anvil cells. The crystal structure of this novel class of compounds was determined via synchrotron single-crystal X-ray diffraction (SCXRD) as well as corroborated by X-ray absorption near edge structure (XANES) measurements and density functional theory (DFT) calculations. The Ln O (CN ) solids are composed of the hitherto unknown CN guanidinate anion-deprotonated guanidine.

Twisted [CO]-groups in Ba[CO] pyrocarbonate.

The inorganic pyrocarbonate salt Ba[CO] contains twisted pyrocarbonate anions ([CO]), an atomic arrangement previously not observed in other pyrocarbonates. This unexpected additional structural degree of freedom points towards an enlarged chemical variability in this novel group of compounds. Ba[CO] was synthesized in a laser-heated diamond anvil cell at 30(2) GPa by heating a mixture of Ba[CO] + CO to ≈ 1500(200) K.

Unraveling the Bonding Complexity of Polyhalogen Anions: High-Pressure Synthesis of Unpredicted Sodium Chlorides NaCl and NaCl and Bromide NaBr.

The field of polyhalogen chemistry, specifically polyhalogen anions (polyhalides), is rapidly evolving. Here, we present the synthesis of three sodium halides with unpredicted chemical compositions and structures (10-NaCl, 18-NaCl, and 18-NaBr), a series of isostructural cubic 8-AX halides (NaCl, KCl, NaBr, and KBr), and a trigonal potassium chloride (24-KCl). The high-pressure syntheses were realized at 41-80 GPa in diamond anvil cells laser-heated at about 2000 K.

High-pressure synthesis of dysprosium carbides.

Chemical reactions between dysprosium and carbon were studied in laser-heated diamond anvil cells at pressures of 19, 55, and 58 GPa and temperatures of ∼2500 K. single-crystal synchrotron X-ray diffraction analysis of the reaction products revealed the formation of novel dysprosium carbides, DyC and DyC, and dysprosium sesquicarbide DyC previously known only at ambient conditions. The structure of DyC was found to be closely related to that of dysprosium sesquicarbide DyC with the PuC-type structure.

Aromatic hexazine [N] anion featured in the complex structure of the high-pressure potassium nitrogen compound KN.

The recent high-pressure synthesis of pentazolates and the subsequent stabilization of the aromatic [N] anion at atmospheric pressure have had an immense impact on nitrogen chemistry. Other aromatic nitrogen species have also been actively sought, including the hexaazabenzene N ring. Although a variety of configurations and geometries have been proposed based on ab initio calculations, one that stands out as a likely candidate is the aromatic hexazine anion [N].

Subduction-related oxidation of the sublithospheric mantle evidenced by ferropericlase and magnesiowüstite diamond inclusions.

Ferropericlase (Mg,Fe)O is the second most abundant mineral in Earth's lower mantle and a common inclusion found in subcratonic diamonds. Pyrolitic mantle has Mg# (100 × Mg/(Mg+Fe)) ~89. However, ferropericlase inclusions in diamonds show a broad range of Mg# between 12 and 93.

High-pressure synthesis of seven lanthanum hydrides with a significant variability of hydrogen content.

The lanthanum-hydrogen system has attracted significant attention following the report of superconductivity in LaH at near-ambient temperatures and high pressures. Phases other than LaH are suspected to be synthesized based on both powder X-ray diffraction and resistivity data, although they have not yet been identified. Here, we present the results of our single-crystal X-ray diffraction studies on this system, supported by density functional theory calculations, which reveal an unexpected chemical and structural diversity of lanthanum hydrides synthesized in the range of 50 to 180 GPa.

Revealing Phosphorus Nitrides up to the Megabar Regime: Synthesis of α'-P N δ-P N and PN.

Invited for the cover of this issue are Dominique Laniel (University of Edinburgh), Florian Trybel (University of Linköping), and their colleagues. The image depicts a bridge built of the newly discovered δ-P N solid with the structure featuring PN units, a previously missing connection between the carbon group elements nitrides and chalcogens nitrides. Read the full text of the article at 10.

FeSiB metallic glass gaskets for high-pressure research beyond 1 Mbar.

A gasket is an important constituent of a diamond anvil cell (DAC) assembly, responsible for the sample chamber stability at extreme conditions for X-ray diffraction studies. In this work, we studied the performance of gaskets made of metallic glass FeSiB in a number of high-pressure X-ray diffraction (XRD) experiments in DACs equipped with conventional and toroidal-shape diamond anvils. The experiments were conducted in either axial or radial geometry with X-ray beams of micrometre to sub-micrometre size.

Revealing Phosphorus Nitrides up to the Megabar Regime: Synthesis of α'-P N δ-P N and PN.

Non-metal nitrides are an exciting field of chemistry, featuring a significant number of compounds that can possess outstanding material properties. These properties mainly rely on maximizing the number of strong covalent bonds, with crosslinked XN octahedra frameworks being particularly attractive. In this study, the phosphorus-nitrogen system was studied up to 137 GPa in laser-heated diamond anvil cells, and three previously unobserved phases were synthesized and characterized by single-crystal X-ray diffraction, Raman spectroscopy measurements and density functional theory calculations.

Anionic N Macrocycles and a Polynitrogen Double Helix in Novel Yttrium Polynitrides YN and Y N at 100 GPa.

Two novel yttrium nitrides, YN and Y N , were synthesized by direct reaction between yttrium and nitrogen at 100 GPa and 3000 K in a laser-heated diamond anvil cell. High-pressure synchrotron single-crystal X-ray diffraction revealed that the crystal structures of YN and Y N feature a unique organization of nitrogen atoms-a previously unknown anionic N macrocycle and a polynitrogen double helix, respectively. Density functional theory calculations, confirming the dynamical stability of the YN and Y N compounds, show an anion-driven metallicity, explaining the unusual bond orders in the polynitrogen units.

Materials synthesis at terapascal static pressures.

Theoretical modelling predicts very unusual structures and properties of materials at extreme pressure and temperature conditions. Hitherto, their synthesis and investigation above 200 gigapascals have been hindered both by the technical complexity of ultrahigh-pressure experiments and by the absence of relevant in situ methods of materials analysis. Here we report on a methodology developed to enable experiments at static compression in the terapascal regime with laser heating.

Sub-micrometer focusing setup for high-pressure crystallography at the Extreme Conditions beamline at PETRA III.

Scientific tasks aimed at decoding and characterizing complex systems and processes at high pressures set new challenges for modern X-ray diffraction instrumentation in terms of X-ray flux, focal spot size and sample positioning. Presented here are new developments at the Extreme Conditions beamline (P02.2, PETRA III, DESY, Germany) that enable considerable improvements in data collection at very high pressures and small scattering volumes.

Testing the performance of secondary anvils shaped with focused ion beam from the single-crystal diamond for use in double-stage diamond anvil cells.

The success of high-pressure research relies on the inventive design of pressure-generating instruments and materials used for their construction. In this study, the anvils of conical frustum or disk shapes with flat or modified culet profiles (toroidal or beveled) were prepared by milling an Ia-type diamond plate made of a (100)-oriented single crystal using the focused ion beam. Raman spectroscopy and synchrotron x-ray diffraction were applied to evaluate the efficiency of the anvils for pressure multiplication in different modes of operation: as single indenters forced against the primary anvil in diamond anvil cells (DACs) or as pairs of anvils forced together in double-stage DACs (dsDACs).