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In this letter, we present electrical and magnetic characteristics of HfO2-based metal-oxide-semiconductor capacitors (MOSCAPs), along with the effect of pseudomorphic Si as a passivating interlayer on GaAs(001) grown by molecular beam epitaxy. Ultrathin HfO2 high-k gate dielectric films (3-15 nm) have been grown on Si/GaAs(001) structures through evaporation of a Hf/HfO2 target in NO2 gas. The lowest interface states density Dit at Au/HfO2/Si/GaAs(001) MOS-structures were obtained in the range of (6-13)×10¹1 eV-1 cm-2 after annealing in the 400-500 °C temperature range as a result of HfO2 crystallization and the Si layer preservation in non-oxidized state on GaAs. HfO2-based MOSCAPs demonstrated the ferromagnetic properties which were attributed to the presence of both cation and anion vacancies according to the first-principle calculations. Room-temperature ferromagnetism in HfO2 films allowed us to propose a structure for the ferromagnetic MOS spin-detector. [ABSTRACT FROM AUTHOR]

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 6 ] rings, and graphitic carbon sheets at high pressure (HP). Here we report the synthesis and structural characterization of a HP-CaC 2 polymorph and a Ca 3 C 7 compound featuring deprotonated polyacene-like and para-poly(indenoindene)-like nanoribbons, respectively. We also demonstrate that carbides with infinite chains of fused [C 6 ] rings can exist even at conditions of deep planetary interiors ( ~ 140 GPa and ~3300 K). Hydrolysis of high-pressure carbides may provide a possible abiotic route to polycyclic aromatic hydrocarbons in Universe., (© 2024. The Author(s).)

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, Sc 2 N 6 , Sc 2 N 8 , ScN 5, and Sc 4 N 3 , synthesized by direct reaction between yttrium and nitrogen at 78-125 GPa and 2500 K in laser-heated diamond anvil cells. High-pressure synchrotron single-crystal X-ray diffraction reveals that in the crystal structures of the nitrogen-rich Sc 2 N 6 , Sc 2 N 8, and ScN 5 phases nitrogen is catenated forming previously unknown N 6 6 - and N 8 6 - units and ∞ 2 ( N 5 3 - ) anionic corrugated 2D-polynitrogen layers consisting of fused N 12 rings. Density functional theory calculations, confirming the dynamical stability of the synthesized compounds, show that Sc 2 N 6 and Sc 2 N 8 possess an anion-driven metallicity, while ScN 5 is an indirect semiconductor. Sc 2 N 6 , Sc 2 N 8 , and ScN 5 solids are promising high-energy-density materials with calculated volumetric energy density, detonation velocity, and detonation pressure higher than those of TNT., (© 2024. The Author(s).)

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. In this study, the high-pressure high-temperature reaction behavior of malononitrile H 2 C(CN) 2 , dicyandiamide (H 2 N) 2 C=NCN, and melamine (C 3 N 3 )(NH 2 ) 3 was investigated in laser-heated diamond anvil cells. Two previously unknown compounds, namely α-C(NH) 2 and β-C(NH) 2 , have been synthesized and found to have fully sp 3 -hybridized carbon atoms. α-C(NH) 2 crystallizes in a distorted β-cristobalite structure, while β-C(NH) 2 is built from previously unknown imide-bridged 2,4,6,8,9,10-hexaazaadamantane units, which form two independent interpenetrating diamond-like networks. Their stability domains and compressibility were studied, for which supporting density functional theory calculations were performed., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Carbon nitrides featuring three-dimensional frameworks of CN 4 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 3 N 4 , hP126-C 3 N 4 , and tI24-CN 2 , in laser-heated diamond anvil cells, is reported. Their structures are solved and refined using synchrotron single-crystal X-ray diffraction. Physical properties investigations show that these strongly covalently bonded materials, ultra-incompressible and superhard, also possess high energy density, piezoelectric, and photoluminescence properties. The novel carbon nitrides are unique among high-pressure materials, as being produced above 100 GPa they are recoverable in air at ambient conditions., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

A series of isostructural Ln 3 O 2 (CN 3 ) (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 3 O 2 (CN 3 ) solids are composed of the hitherto unknown CN 3 5- guanidinate anion-deprotonated guanidine. Changes in unit cell volumes and compressibility of Ln 3 O 2 (CN 3 ) (Ln=La, Eu, Gd, Tb, Ho, Yb) compounds are found to be dictated by the lanthanide contraction phenomenon. Decompression experiments show that Ln 3 O 2 (CN 3 ) compounds are recoverable to ambient conditions. The stabilization of the CN 3 5- guanidinate anion at ambient conditions provides new opportunities in inorganic and organic synthetic chemistry., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

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. In situ single-crystal synchrotron X-ray diffraction analysis of the reaction products revealed the formation of novel dysprosium carbides, Dy 4 C 3 and Dy 3 C 2 , and dysprosium sesquicarbide Dy 2 C 3 previously known only at ambient conditions. The structure of Dy 4 C 3 was found to be closely related to that of dysprosium sesquicarbide Dy 2 C 3 with the Pu 2 C 3 -type structure. Ab initio calculations reproduce well crystal structures of all synthesized phases and predict their compressional behavior in agreement with our experimental data. Our work gives evidence that high-pressure synthesis conditions enrich the chemistry of rare earth metal carbides., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Akbar, Aslandukova, Aslandukov, Yin, Trybel, Khandarkhaeva, Fedotenko, Laniel, Bykov, Bykova, Dubrovinskaia and Dubrovinsky.)

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 ( tP 10-Na 2 Cl 3 , hP 18-Na 4 Cl 5 , and hP 18-Na 4 Br 5 ), a series of isostructural cubic cP 8-AX 3 halides (NaCl 3 , KCl 3 , NaBr 3 , and KBr 3 ), and a trigonal potassium chloride ( hP 24-KCl 3 ). The high-pressure syntheses were realized at 41-80 GPa in diamond anvil cells laser-heated at about 2000 K. Single-crystal synchrotron X-ray diffraction (XRD) provided the first accurate structural data for the symmetric trichloride Cl 3 - anion in hP 24-KCl 3 and revealed the existence of two different types of infinite linear polyhalogen chains, [Cl] ∞ n - and [Br] ∞ n - , in the structures of cP 8-AX 3 compounds and in hP 18-Na 4 Cl 5 and hP 18-Na 4 Br 5 . In Na 4 Cl 5 and Na 4 Br 5 , we found unusually short, likely pressure-stabilized, contacts between sodium cations. Ab initio calculations support the analysis of structures, bonding, and properties of the studied halogenides., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The recent high-pressure synthesis of pentazolates and the subsequent stabilization of the aromatic [N 5 ] - 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 6 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 6 ] 4- . Here we present the synthesis of this species, realized in the high-pressure potassium nitrogen compound K 9 N 56 formed at high pressures (46 and 61 GPa) and high temperature (estimated to be above 2,000 K) by direct reaction between nitrogen and KN 3 in a laser-heated diamond anvil cell. The complex structure of K 9 N 56 -composed of 520 atoms per unit cell-was solved based on synchrotron single-crystal X-ray diffraction and corroborated by density functional theory calculations. The observed hexazine anion [N 6 ] 4- is planar and proposed to be aromatic., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

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. Here we use Synchrotron Mössbauer Source (SMS) spectroscopy and single-crystal X-ray diffraction to determine the iron oxidation state and structure of two magnesiowüstite and three ferropericlase inclusions in diamonds from São Luiz, Brazil. Inclusion Mg#s vary between 16.1 and 84.5. Ferropericlase inclusions contain no ferric iron within the detection limit of SMS, while both magnesiowüstite inclusions show the presence of monocrystalline magnesioferrite ((Mg,Fe)Fe 3+ 2 O 4 ) with an estimated 47-53 wt% Fe 2 O 3 . We argue that the wide range of Fe concentrations observed in (Mg,Fe)O inclusions in diamonds and the appearance of magnesioferrite result from oxidation of ferropericlase triggered by the introduction of subducted material into sublithospheric mantle., (© 2022. The Author(s).)

The lanthanum-hydrogen system has attracted significant attention following the report of superconductivity in LaH 10 at near-ambient temperatures and high pressures. Phases other than LaH 10 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. Seven lanthanum hydrides were produced, LaH 3 , LaH ~4 , LaH 4+δ , La 4 H 23 , LaH 6+δ , LaH 9+δ , and LaH 10+δ , and the atomic coordinates of lanthanum in their structures determined. The regularities in rare-earth element hydrides unveiled here provide clues to guide the search for other synthesizable hydrides and candidate high-temperature superconductors. The hydrogen content variability in lanthanum hydrides and the samples' phase heterogeneity underline the challenges related to assessing potentially superconducting phases and the nature of electronic transitions in high-pressure hydrides., (© 2022. The Author(s).)

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 3 N 5 solid with the structure featuring PN 6 units, a previously missing connection between the carbon group elements nitrides and chalcogens nitrides. Read the full text of the article at 10.1002/chem.202201998., (© 2022 Wiley-VCH GmbH.)

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 Fe 0.79 Si 0.07 B 0.14 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. We report that Fe 0.79 Si 0.07 B 0.14 metallic glass gaskets offer a stable sample environment under compression exceeding 1 Mbar in all XRD experiments described here, even in those involving small-molecule gases (e.g. Ne, H 2 ) used as pressure-transmitting media or in those with laser heating in a DAC. Our results emphasize the material's importance for a great number of delicate experiments conducted under extreme conditions. They indicate that the application of Fe 0.79 Si 0.07 B 0.14 metallic glass gaskets in XRD experiments for both axial and radial geometries substantially improves various aspects of megabar experiments and, in particular, the signal-to-noise ratio in comparison to that with conventional gaskets made of Re, W, steel or other crystalline metals., (open access.)

Two novel yttrium nitrides, YN 6 and Y 2 N 11 , 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 6 and Y 2 N 11 feature a unique organization of nitrogen atoms-a previously unknown anionic N 18 macrocycle and a polynitrogen double helix, respectively. Density functional theory calculations, confirming the dynamical stability of the YN 6 and Y 2 N 11 compounds, show an anion-driven metallicity, explaining the unusual bond orders in the polynitrogen units. As the charge state of the polynitrogen double helix in Y 2 N 11 is different from that previously found in Hf 2 N 11 and because N 18 macrocycles have never been predicted or observed, their discovery significantly extends the chemistry of polynitrides., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The experimental study of hydrogen-bonds and their symmetrization under extreme conditions is predominantly driven by diffraction methods, despite challenges of localising or probing the hydrogen subsystems directly. Until recently, H-bond symmetrization has been addressed in terms of either nuclear quantum effects, spin crossovers or direct structural transitions; often leading to contradictory interpretations when combined. Here, we present high-resolution in-situ 1 H-NMR experiments in diamond anvil cells investigating a range of systems containing linear O-H ⋯  O units at pressure ranges of up to 90 GPa covering their respective H-bond symmetrization. We found pronounced minima in the pressure dependence of the NMR resonance line-widths associated with a maximum in hydrogen mobility, precursor to a localisation of hydrogen atoms. These minima, independent of the chemical environment of the O-H ⋯  O unit, can be found in a narrow range of oxygen oxygen distances between 2.44 and 2.45 Å, leading to an average critical oxygen-oxygen distance of [Formula: see text] Å., (© 2022. The Author(s).)

Theoretical modelling predicts very unusual structures and properties of materials at extreme pressure and temperature conditions 1,2 . 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. We apply this method to realize pressures of about 600 and 900 gigapascals in a laser-heated double-stage diamond anvil cell 3 , producing a rhenium-nitrogen alloy and achieving the synthesis of rhenium nitride Re 7 N 3 -which, as our theoretical analysis shows, is only stable under extreme compression. Full chemical and structural characterization of the materials, realized using synchrotron single-crystal X-ray diffraction on microcrystals in situ, demonstrates the capabilities of the methodology to extend high-pressure crystallography to the terapascal regime., (© 2022. The Author(s).)

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). All types of secondary anvils performed well up to about 250 GPa. The pressure multiplication factor of single indenters appeared to be insignificantly dependent on the shape of the anvils and their culets' profiles. The enhanced pressure multiplication factor found for pairs of toroidally shaped secondary anvils makes this design very promising for ultrahigh-pressure experiments in dsDACs.

Magnetite, Fe 3 O 4 , is the oldest known magnetic mineral and archetypal mixed-valence oxide. Despite its recognized role in deep Earth processes, the behavior of magnetite at extreme high-pressure high-temperature (HPHT) conditions remains insufficiently studied. Here, we report on single-crystal synchrotron X-ray diffraction experiments up to ∼80 GPa and 5000 K in diamond anvil cells, which reveal two previously unknown Fe 3 O 4 polymorphs, γ-Fe 3 O 4 with the orthorhombic Yb 3 S 4 -type structure and δ-Fe 3 O 4 with the modified Th 3 P 4 -type structure. The latter has never been predicted for iron compounds. The decomposition of Fe 3 O 4 at HPHT conditions was found to result in the formation of exotic phases, Fe 5 O 7 and Fe 25 O 32 , with complex structures. Crystal-chemical analysis of iron oxides suggests the high-spin to low-spin crossover in octahedrally coordinated Fe 3+ in the pressure interval between 43 and 51 GPa. Our experiments demonstrate that HPHT conditions promote the formation of ferric-rich Fe-O compounds, thus arguing for the possible involvement of magnetite in the deep oxygen cycle.

Changes in the bonding of carbon under high pressure leads to unusual crystal chemistry and can dramatically alter the properties of transition metal carbides. In this work, the new orthorhombic polymorph of yttrium carbide, γ-Y&#95;{4}C&#95;{5}, was synthesized from yttrium and paraffin oil in a laser-heated diamond anvil cell at ∼50  GPa. The structure of γ-Y&#95;{4}C&#95;{5} was solved and refined using in situ synchrotron single-crystal x-ray diffraction. It includes two carbon groups: [C&#95;{2}] dimers and nonlinear [C&#95;{3}] trimers. Crystal chemical analysis and density functional theory calculations revealed unusually high noninteger charges ([C&#95;{2}]^{5.2-} and [C&#95;{3}]^{6.8-}) and unique bond orders (<1.5). Our results extend the list of possible carbon states at extreme conditions.

In contrast to the corundum-type A 2 X 3 structure, which has only one crystallographic site available for trivalent cations (e.g., in hematite), the closely related ABX 3 ilmenite-type structure comprises two different octahedrally coordinated positions that are usually filled with differently charged ions (e.g., in Fe 2+ Ti 4+ O 3 ilmenite). Here, we report a synthesis of the first binary ilmenite-type compound fabricated from a simple transition-metal oxide (Mn 2 O 3 ) at high-pressure high-temperature (HP-HT) conditions. We experimentally established that, at normal conditions, the ilmenite-type Mn 2+ Mn 4+ O 3 (ε-Mn 2 O 3 ) is an n-type semiconductor with an indirect narrow band gap of E g = 0.55 eV. Comparative investigations of the electronic properties of ε-Mn 2 O 3 and previously discovered quadruple perovskite ζ-Mn 2 O 3 phase were performed using X-ray absorption near edge spectroscopy. Magnetic susceptibility measurements reveal an antiferromagnetic ordering in ε-Mn 2 O 3 below 210 K. The synthesis of ε-Mn 2 O 3 indicates that HP-HT conditions can induce a charge disproportionation in simple transition-metal oxides A 2 O 3 , and potentially various mixed-valence polymorphs of these oxides, for example, with ilmenite-type, LiNbO 3 -type, perovskite-type, and other structures, could be stabilized at HP-HT conditions.

We synthesized single crystals of marokite (CaMn 2 O 4 )-type orthorhombic manganese (II,III) oxide, γ-Mn 3 O 4 , in a multianvil apparatus at pressures of 10-24 GPa. The magnetic, electronic, and optical properties of the crystals were investigated at ambient pressure. It was found that γ-Mn 3 O 4 is a semiconductor with an indirect band gap E g of 0.96 eV and two antiferromagnetic transitions ( T N ) at ∼200 and ∼55 K. The phase stability of the γ-Mn 3 O 4 crystals was examined in the pressure range of 0-60 GPa using single-crystal X-ray diffraction and Raman spectroscopy. A bulk modulus of γ-Mn 3 O 4 was determined to be B 0 = 235.3(2) GPa with B ' = 2.6(6). The γ-Mn 3 O 4 phase persisted over the whole pressure range studied and did not transform or decompose upon laser heating of the sample to ∼3500 K at 60 GPa. This result seems surprising, given the high-pressure structural diversity of iron oxides with similar stoichiometries. With an increase in pressure, the degree of distortion of MnO 6 polyhedra decreased. Furthermore, there are signs indicating a limited charge transfer between the Mn 3+ ions in the octahedra and the Mn 2+ ions in the trigonal prisms. Our results demonstrate that the high-pressure behavior of the structural, electronic, and chemical properties of manganese oxides strongly differs from that of iron oxides with similar stoichiometries.

One of the most striking properties of molecular hydrogen is the coupling between molecular rotational properties and nuclear spin orientations, giving rise to the spin isomers ortho- and para-hydrogen. At high pressure, as intermolecular interactions increase significantly, the free rotation of H 2 molecules is increasingly hindered, and consequently a modification of the coupling between molecular rotational properties and the nuclear spin system can be anticipated. To date, high-pressure experimental methods have not been able to observe nuclear spin states at pressures approaching 100 GPa (Meier, Annu. Rep. NMR Spectrosc. 94:1-74, 2017; Meier, Prog. Nucl. Magn. Reson. Spectrosc. 106-107:26-36, 2018) and consequently the effect of high pressure on the nuclear spin statistics could not be directly measured. Here, we present in-situ high-pressure nuclear magnetic resonance data on molecular hydrogen in its hexagonal phase I up to 123 GPa at room temperature. While our measurements confirm the presence of ortho-hydrogen at low pressures, above 70 GPa, we observe a crossover in the nuclear spin statistics from a spin-1 quadrupolar to a spin-1/2 dipolar system, evidencing the loss of spin isomer distinction. These observations represent a unique case of a nuclear spin crossover phenomenon in quantum solids.

Polynitrides are intrinsically thermodynamically unstable at ambient conditions and require peculiar synthetic approaches. Now, a one-step synthesis of metal-inorganic frameworks Hf 4 N 20 ⋅N 2 , WN 8 ⋅N 2 , and Os 5 N 28 ⋅3 N 2 via direct reactions between elements in a diamond anvil cell at pressures exceeding 100 GPa is reported. The porous frameworks (Hf 4 N 20 , WN 8 , and Os 5 N 28 ) are built from transition-metal atoms linked either by polymeric polydiazenediyl (polyacetylene-like) nitrogen chains or through dinitrogen units. Triply bound dinitrogen molecules occupy channels of these frameworks. Owing to conjugated polydiazenediyl chains, these compounds exhibit metallic properties. The high-pressure reaction between Hf and N 2 also leads to a non-centrosymmetric polynitride Hf 2 N 11 that features double-helix catena-poly[tetraz-1-ene-1,4-diyl] nitrogen chains [-N-N-N=N-] ∞ ., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Three binary fcc -structured alloys ( fcc -Ir 0.50 Pt 0.50 , fcc -Rh 0.66 Pt 0.33 and fcc -Rh 0.50 Pd 0.50 ) were prepared from [Ir(NH 3 ) 5 Cl][PtCl 6 ], [Ir(NH 3 ) 5 Cl][PtBr 6 ], [Rh(NH 3 ) 5 Cl] 2 [PtCl 6 ]Cl 2 and [Rh(NH 3 ) 5 Cl][PdCl 4 ]·H 2 O, respectively, as single-source precursors. All alloys were prepared by thermal decomposition in gaseous hydrogen flow below 800 °C. Fcc -Ir 0.50 Pt 0.50 and fcc -Rh 0.50 Pd 0.50 correspond to miscibility gaps on binary metallic phase diagrams and can be considered as metastable alloys. Detailed comparison of [Ir(NH 3 ) 5 Cl][PtCl 6 ] and [Ir(NH 3 ) 5 Cl][PtBr 6 ] crystal structures suggests that two isoformular salts are not isostructural. In [Ir(NH 3 ) 5 Cl][PtBr 6 ], specific Br…Br interactions are responsible for a crystal structure arrangement. Room temperature compressibility of fcc -Ir 0.50 Pt 0.50 , fcc -Rh 0.66 Pt 0.33 and fcc -Rh 0.50 Pd 0.50 has been investigated up to 50 GPa in diamond anvil cells. All investigated fcc -structured binary alloys are stable under compression. Atomic volumes and bulk moduli show good agreement with ideal solutions model. For fcc -Ir 0.50 Pt 0.50 , V 0 / Z = 14.597(6) Å 3 ·atom -1 , B 0 = 321(6) GPa and B 0 ' = 6(1); for fcc -Rh 0.66 Pt 0.33 , V 0 / Z = 14.211(3) Å 3 ·atom -1 , B 0 =259(1) GPa and B 0 ' = 6.66(9) and for fcc -Rh 0.50 Pd 0.50 , V 0 / Z = 14.18(2) Å 3 ·atom -1 , B 0 =223(4) GPa and B 0 ' = 5.0(3).

High pressure Nuclear Magnetic Resonance (NMR) is known to reveal the behavior of matter under extreme conditions. However, until now, significant maintenance demands, space requirements, and high costs of superconducting magnets render its application unfeasible for regular modern high pressure laboratories. Here, we present a table-top NMR system based on permanent Halbach magnet arrays with a diameter of 25 cm and height of 4 cm. At the highest field of 1013 mT, 1 H-NMR spectra of ice VII have been recorded at 25 GPa and ambient temperature. The table-top NMR system can be used together with double sided laser heating setups. Feasibility of high-pressure high-temperature NMR was demonstrated by collecting 1 H-NMR spectra of H 2 O at 25 GPa and 1063(50) K. The change in the signal intensity in a laser-heated NMR diamond anvil cell has been found to yield a convenient way for temperature measurements.

Iron tetra-nitride, FeN 4 , was synthesized from the elements in a laser-heated diamond anvil cell at 180 (5) GPa and 2700 (200) K. Its crystal structure was determined based on single-crystal X-ray diffraction data collected from a submicron-sized grain at the synchrotron beamline ID11 of ESRF. The compound crystallizes in the triclinic space group P . In the asymmetric unit, the Fe atom occupies an inversion centre (Wyckoff position 1 d ), while two N atoms occupy general positions (2 i ). The structure is made up from edge-sharing [FeN 6 ] octa-hedra forming chains along [100] and being inter-connected through N-N bridges. N atoms form catena -poly[tetraz-1-ene-1,4-di-yl] anions [-N=N-N-N-] ∞ 2- running along [001]. In comparison with the previously reported structure of FeN 4 at 135 GPa [Bykov et al. (2018). Nat. Commun. 9 , 2756], the crystal structure of FeN 4 at 180 GPa is similar but the structural model is significantly improved in terms of the precision of the bond lengths and angles.

Hydrogen bond symmetrisations in H-bonded systems triggered by pressure-induced nuclear quantum effects (NQEs) is a long-known concept but experimental evidence in high-pressure ices has remained elusive with conventional methods. Theoretical works predicted quantum-mechanical tunneling of protons within water ices to occur at pressures above 30 GPa, and the H-bond symmetrisation transition to occur above 60 GPa. Here we used 1 H-NMR on high-pressure ice up to 97 GPa, and demonstrate that NQEs govern the behavior of the hydrogen bonded protons in ice VII already at significantly lower pressures than previously expected. A pronounced tunneling mode was found to be present up to the highest pressures of 97 GPa, well into the stability field of ice X, where NQEs are not anticipated in a fully symmetrised H-bond network. We found two distinct transitions in the NMR shift data at about 20 GPa and 75 GPa attributed to the step-wise symmetrisation of the H-bond.

The past 15 years have seen an astonishing increase in Nuclear Magnetic Resonance (NMR) sensitivity and accessible pressure range in high-pressure NMR experiments, owing to a series of new developments of NMR spectroscopy applied to the diamond anvil cell (DAC). Recently, with the application of electro-magnetic lenses, so-called Lenz lenses, in toroidal diamond indenter cells, pressures of up to 72 GPa with NMR spin sensitivities of about 10 12  spin/Hz 1/2 has been achieved. Here, we describe the implementation of a refined NMR resonator structure using a pair of double stage Lenz lenses driven by a Helmholtz coil within a standard DAC, allowing to measure sample volumes as small as 100 pl prior to compression. With this set-up, pressures close to 100 GPa could be realised repeatedly, with enhanced spin sensitivities of about 5 × 10 11 spin/Hz 1/2 . The manufacturing and handling of these new NMR-DACs is relatively easy and straightforward, which will allow for further applications in physics, chemistry, or biochemistry., (Copyright © 2018 Elsevier Inc. All rights reserved.)