Polymorphism of pyrene on compression to 35 GPa in a diamond anvil cell.

Structural studies of pyrene have been limited to below 2 GPa. Here, we report on investigations of pyrene up to ~35 GPa using in situ single-crystal synchrotron X-ray diffraction in diamond anvil cells and ab initio calculations. They reveal the phase transitions from pyrene-I to pyrene-II (0.

High-Pressure 16-YBr Polymorph Recoverable to Ambient Conditions: From 3D Framework to Layered Material.

Exfoliation of graphite and the discovery of the unique properties of graphene─graphite's single layer─have raised significant attention to layered compounds as potential precursors to 2D materials with applications in optoelectronics, spintronics, sensors, and solar cells. In this work, a new orthorhombic polymorph of yttrium bromide, 16-YBr was synthesized from yttrium and CBr in a laser-heated diamond anvil cell at 45 GPa and 3000 K. The structure of 16-YBr was solved and refined using in situ synchrotron single-crystal X-ray diffraction.

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.

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.

Stabilization of N and N anionic units and 2D polynitrogen layers in high-pressure scandium polynitrides.

Nitrogen catenation under high pressure leads to the formation of polynitrogen compounds with potentially unique properties. The exploration of the entire spectrum of poly- and oligo-nitrogen moieties is still in its earliest stages. Here, we report on four novel scandium nitrides, ScN, ScN, ScN and ScN, synthesized by direct reaction between yttrium and nitrogen at 78-125 GPa and 2500 K in laser-heated diamond anvil cells.

Simple Molecules under High-Pressure and High-Temperature Conditions: Synthesis and Characterization of α- and β-C(NH) with Fully sp -Hybridized Carbon.

The elements hydrogen, carbon, and nitrogen are among the most abundant in the solar system. Still, little is known about the ternary compounds these elements can form under the high-pressure and high-temperature conditions found in the outer planets' interiors. These materials are also of significant research interest since they are predicted to feature many desirable properties such as high thermal conductivity and hardness due to strong covalent bonding networks.

Crystal chemistry and compressibility of FeMgAlSiO and FeMgSiO silicate perovskites at pressures up to 95 GPa.

Silicate perovskite, with the mineral name bridgmanite, is the most abundant mineral in the Earth's lower mantle. We investigated crystal structures and equations of state of two perovskite-type Fe-rich phases, FeMgSiO and FeMgAlSiO, at high pressures, employing single-crystal X-ray diffraction and synchrotron Mössbauer spectroscopy. We solved their crystal structures at high pressures and found that the FeMgSiO phase adopts a novel monoclinic double-perovskite structure with the space group of at pressures above 12 GPa, whereas the FeMgAlSiO phase adopts an orthorhombic perovskite structure with the space group of at pressures above 8 GPa.

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 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.

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.

Electronic properties of single-crystalline FeO.

We synthesized single and polycrystals of iron oxide with an unconventional FeO stoichiometry under high-pressure high-temperature (HP-HT) conditions. The crystals of FeO had a CaFeO-type structure composed of linear chains of iron with octahedral and trigonal-prismatic oxygen coordinations. We investigated the electronic properties of this mixed-valence oxide using several experimental techniques, including measurements of electrical resistivity, the Hall effect, magnetoresistance, and thermoelectric power (Seebeck coefficient), X-ray absorption near edge spectroscopy (XANES), reflectance and absorption spectroscopy, and single-crystal X-ray diffraction.

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].

Synthesis of rare-earth metal compounds through enhanced reactivity of alkali halides at high pressures.

Chemical stability of the alkali halides NaCl and KCl has allowed for their use as inert media in high-pressure high-temperature experiments. Here we demonstrate the unexpected reactivity of the halides with metals (Y, Dy, and Re) and iron oxide (FeO) in a laser-heated diamond anvil cell, thus providing a synthetic route for halogen-containing binary and ternary compounds. So far unknown chlorides, YCl and DyCl, and chloride carbides, YClC and DyClC, were synthesized at ~40 GPa and 2000 K and their structures were solved and refined using in situ single-crystal synchrotron X-ray diffraction.

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.

() program: the analysis of single-crystal X-ray diffraction data from polycrystalline samples.

This paper presents the () program and its application to the analysis of single-crystal X-ray diffraction (SC-XRD) data from multiphase mixtures of microcrystalline solids and powders. Superposition of numerous reflections originating from a large number of single-crystal domains of the same and/or different (especially unknown) phases usually precludes the sorting of reflections coming from individual domains, making their automatic indexing impossible. The algorithm is designed to quickly find subsets of reflections from individual domains in a whole set of SC-XRD data.

Novel Class of Rhenium Borides Based on Hexagonal Boron Networks Interconnected by Short B Dumbbells.

Transition metal borides are known due to their attractive mechanical, electronic, refractive, and other properties. A new class of rhenium borides was identified by synchrotron single-crystal X-ray diffraction experiments in laser-heated diamond anvil cells between 26 and 75 GPa. Recoverable to ambient conditions, compounds rhenium triboride (ReB) and rhenium tetraboride (ReB) consist of close-packed single layers of rhenium atoms alternating with boron networks built from puckered hexagonal layers, which link short bonded (∼1.

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.