Search

The high-pressure behaviour and the crystal-fluid interaction of zeolites with EAB topology were investigated by in-situ single-crystal and powder synchrotron X-ray diffraction, both on synthetic and natural samples. The experiments were conducted using a diamond anvil cell and different pressure transmitting fluids, including: the non-penetrating silicone oil and the potentially penetrating methanol : ethanol : H 2 O = 16:3:1 mixture, methanol and distilled H 2 O. The zeolites intrinsic compressional behaviour investigated with a non-penetrating fluid showed the significant role of the extra framework population on the bulk compressibility. Notably, within the first ∼0.5 GPa of the silicone oil ramp, the bulk modulus (K V0 = β V0 −1) resulted to be K V0 = 62(1) GPa for the natural bellbergite and K V0 = 16(4) GPa for the synthetic K-analogue. The synthetic EAB zeolites demonstrated a high host capacity for methanol molecules, which were not able to penetrate the natural bellbergite cavities. A comparative analysis between the behaviour of zeolites with EAB topology and structurally similar zeolites, such as erionite (ERI topology) and offretite (OFF), is provided. [Display omitted] • Natural and synthetic EAB zeolites were studied under in-situ high- P conditions. • Only synthetic EABs show P -mediated intrusion of methanol molecules at few kbar. • Only a modest crystal-fluid interaction occurs in the natural sample. • Synthetic EABs are suitable for the P -induced hyper-confinement of guest molecules. [ABSTRACT FROM AUTHOR]

The compressional behaviour of a natural allanite from Lago della Vecchia (upper Cervo valley, Italy) metagranitoids [A1( Ca 0.69 Fe 0.31 2 + )Σ1.00A2(Ca0.46Ce0.24La0.12Sm0.02Pr0.05Nd0.09Th0.02)Σ1.00M1( Al 0.65 Fe 0.34 3 + Ti0.02)Σ1.01M2(Al0.99)M3( Fe 0.54 3 + Fe 0.36 2 + Mg0.06 Ti 0.02 4 + Al0.01)Σ0.99Si1,Si2,Si3(Si2.80Al0.20)Σ3.00O11(OH,O)] has been investigated up to 16 GPa (at 298 K) by means of in situ synchrotron single-crystal X-ray diffraction. Experiments have been conducted under hydrostatic conditions, using a diamond anvil cell and the mix methanol:ethanol:water = 16:3:1 (up to 10 GPa) and neon (up to 16 GPa) as pressure-transmitting media. No phase transition has been observed within the pressure-range investigated. Data collected in decompression prove that, at least up to 16 GPa (at 298 K), the deformation mechanisms are fully reversible. A third-order Birch–Murnaghan Equation of State (BM-EoS) was fitted to the P–V data (up to 10 GPa), giving: V0 = 470.2(2) Å3, KP0,T0 = 131(4) GPa and K′= 1.9(8). The evolution of the lattice parameters with pressure shows a slight anisotropic compression pattern, with KP0,T0(a):KP0,T0(b):KP0,T0(c) = 1.24:1.52:1. The monoclinic β-angle decreases monotonically with pressure, with: βP(°) = βP0 – 0.0902(4)P (R2 = 0.997, with P in GPa). The main deformation mechanisms at the atomic scale are described based on a series of structure refinements at different pressures. A comparison between the compressional behavior of allanite, epidote and clinozoisite is carried out. [ABSTRACT FROM AUTHOR]

Abstract The pressure-induced amorphization of the two endmembers of the plagioclase ((Na 1− x Ca x)Al 1+ x Si 3− x O 8) solid-solution, anorthite (CaAl 2 Si 2 O 8) and albite (NaAlSi 3 O 8), has been studied as a function of compression rate by means of time-resolved powder diffraction. Anorthite and albite were compressed in a diamond anvil cell to 80 GPa at multiple rates from 0.05 GPa/s to 80 GPa/s. The amorphization pressure decreases with increasing compression rate. This negative strain rate sensitivity indicates a change in deformation mechanism in the plagioclase solid-solution endmembers from brittle to ductile with increasing compression rate. The presented data support the previously proposed shear deformation mechanism for the amorphization of plagioclase. Furthermore, amorphization progresses over a wide pressure range suggesting heterogeneous amorphization, similar to observations based on recovered material from shock-compression experiments of plagioclase. Our experiments support the contention that amorphization pressures for plagioclase may occur at lower pressures than usually considered. Highlights • Amorphization pressures in plagioclase decrease with increasing compression rate. • In situ rapid compression experiments support a shear induced deformation model. • Amorphous plagioclase is not an unambiguous standard for peak pressure in impacts. [ABSTRACT FROM AUTHOR]

The P-T phase stability field, the thermoelastic behavior and the P-induced deformation mechanisms at the atomic scale of pargasite crystals, from the “phlogopite peridotite unit” of the Finero mafic-ultramafic complex (Ivrea-Verbano Formation, Italy), have been investigated by a series of in situ experiments: (a) at high pressure (up to 20.1 GPa), by single-crystal synchrotron X-ray diffraction with a diamond anvil cell, (b) at high temperature (up to 823 K), by powder synchrotron X-ray diffraction using a hot air blower device, and (c) at simultaneous HP-HT conditions, by single-crystal synchrotron X-ray diffraction with a resistive-heated diamond anvil cell (Pmax = 16.5 GPa, Tmax = 1200 K). No phase transition has been observed within the P-T range investigated. At ambient T, the refined compressional parameters, calculated by fitting a second-order Birch-Murnaghan Equation of State (BM-EoS), are: V0 = 915.2(8) Å3 and KP0,T0 = 95(2) GPa (βP0,T0 = 0.0121(2) GPa−1) for the unit-cell volume; a0 = 9.909(4) Å and K(a)P0,T0 = 76(2) GPa for the a-axis; b0 = 18.066(7) Å and K(b)P0,T0 = 111(2) GPa for the b-axis; c0 = 5.299(5) Å and K(c)P0,T0 = 122(12) GPa for the c-axis [K(c)P0,T0 ~ K(b)P0,T0 > K(a)P0,T0]. The high-pressure structure refinements (at ambient T) show a moderate contraction of the TO4 double chain and a decrease of its bending in response to the hydrostatic compression, along with a pronounced compressibility of the A- and M(4)-polyhedra [KP0,T0(A) = 38(2) GPa, KP0,T0(M4) = 79(5) GPa] if compared to the M(1)-, M(2)-, M(3)-octahedra [KP0,T0(M1,2,3) ≤ 120 GPa] and to the rigid tetrahedra [KP0,T0(T1,T2) ~ 300 GPa]. The thermal behavior, at ambient pressure up to 823 K, was modelled with Berman’s formalism, which gives: V0 = 909.1(2) Å3, α0 = 2.7(2)·10−5 K−1 and α1 = 1.4(6)·10−9 K−2 [with α0(a) = 0.47(6)·10−5 K−1, α0(b) = 1.07(4)·10−5 K−1, and α0(c) = 0.97(7)·10−5 K−1]. The petrological implications for the experimental findings of this study are discussed. [ABSTRACT FROM AUTHOR]

The iron spin crossover in ferropericlase, the second most abundant mineral in Earth's lower mantle, causes changes in a range of physical properties, including seismic wave velocities. Understanding the effect of temperature on the spin crossover is essential to detect its signature in seismic observations and constrain its occurrence in the mantle. Here, we report the first experimental results on the spin crossover-induced bulk modulus softening at high temperatures, derived directly from time-resolved x-ray diffraction measurements during continuous compression of (Mg 0.8 Fe 0.2)O in a resistive-heated dynamic diamond-anvil cell. We present new theoretical calculations of the spin crossover at mantle temperatures benchmarked by the experiments. Based on our results, we create synthetic seismic tomography models to investigate the signature of the spin crossover in global seismic tomography. A tomographic filter is applied to allow for meaningful comparisons between the synthetic models and data-based seismic tomography models, like SP12RTS. A negative anomaly in the correlation between V s variations and V c variations (S-C correlation) is found to be the most suitable measure to detect the presence of the spin crossover in tomographic models. When including the effects of the spin crossover, the misfit between the synthetic model and SP12RTS is reduced by 63%, providing strong evidence for the presence of the spin crossover, and hence ferropericlase, in the lower mantle. Future improvement of seismic resolution may facilitate a detailed mapping of spin state using the S-C correlation, providing constraints on mantle temperatures by taking advantage of the temperature sensitivity of the spin crossover. • First measurements of the elastic softening in ferropericlase at high temperature. • New theoretical calculations of the iron spin crossover benchmarked by experiments. • Signature in seismic tomography investigated using synthetic tomography models. • Synthetic models with a realistic resolution are compared to data-based models. • Evidence for the presence of mixed-spin ferropericlase in Earth's lower mantle. [ABSTRACT FROM AUTHOR]

The elastic behavior and the structural evolution at high pressure of a natural phillipsite have been investigated by in situ single-crystal X-ray diffraction up to 9.44 GPa, using a diamond anvil cell and the nominally penetrating P-transmitting fluid methanol:ethanol:water (16:3:1) mix. Although no phase transition was observed within the P-range investigated, two different compressional regimes occur. Between 0.0001 and 2.0 GPa, the refined elastic parameters, calculated by a second-order Birch-Murnaghan equation of state (BM-EoS) fit, are V = 1005(1) Å, K = 89(8) GPa for the unit-cell volume; a = 9.914(7) Å, K = 81(12) GPa for the a-axis; b = 14.201(9) Å, K = 50(5) GPa for the b-axis; and c = 8.707(2) Å, K = 107(8) GPa for the c-axis ( K : K : K ~1.62:1:2.14). Between 2.0 and 9.4 GPa, a P-induced change in the configuration of HO molecules, coupled with a change in the tilting mechanisms of the framework tetrahedra, gives rise to a second compressional regime, in which the phillipsite structure is softer if compared to the first compressional range. In the second compressional regime, the refined elastic parameters, calculated by a second-order BM-EoS fit, are V = 1098 (7) Å, K = 18.8(7) GPa for the unit-cell volume; a = 10.07(3) Å, K = 30(2) GPa for the a-axis; b = 14.8(1) Å, K = 11(1) GPa for the b-axis; and c = 8.94(2) Å, K = 21(1) GPa for the c-axis ( K : K : K ~2.72:1:1.90). The evolution of the monoclinic β angle with pressure shows two distinct trends in the two compressional regimes: with a negative slope between 0.0001 and 2.0 GPa, and a positive slope between 2.0 and 9.4 GPa. The mechanisms, at the atomic scale, that govern the two compressional regimes of the phillipsite structure are described. [ABSTRACT FROM AUTHOR]

The high-pressure behaviour and the crystal-fluid interaction of a natural offretite have been investigated by in situ single-crystal synchrotron X-ray diffraction, using a diamond anvil cell. Five different P -transmitting fluids have been employed: the non penetrating daphne oil 7575 and the potentially penetrating methanol:ethanol:H 2 O ​= ​16:3:1 mixture, ethanol:water ​= ​1:1 mixture, distilled H 2 O and liquid Ne. The daphne oil 7575 experiment allowed to describe the intrinsic compressional behaviour of offretite, without any pressure-induced crystal-fluid interaction, with an isothermal bulk modulus K V 0 ​= ​59(2) GPa (β V 0 ​= ​0.0170(9) GPa−1) for the range P amb -1.83(5) GPa. All the experiments in potentially penetrating P -transmitting fluids showed the P -induced sorption of extra molecules within the large 12 ​mRs channel of offretite, obtained on the basis of X-ray structure refinements. For the aqueous mixtures, the magnitude of the adsorption appears to be governed by the H 2 O content of the P -transmitting fluid. Ne atoms are also able to penetrate into the 12 ​mRs channel in response to the applied pressure, interacting with the extraframework population via weak Van der Waals attraction. A comparative analysis of the P -mediated crystal-fluid interaction phenomena between offretite and the structurally similar erionite is provided. [Display omitted] • The compressional behaviour of offretite was studies by synchrotron SC-XRD. • Alcohols-water mixes and liquid Ne were used as P -transmitting fluids. • P -mediated selective adsorption of molecules (from the mixes) was observed. • P -mediated intrusion of Ne atoms occurred within the large 12 ​mRs channel. [ABSTRACT FROM AUTHOR]

The '660' discontinuity is often associated with a phase transitions in pyrolite at about 24 GPa. There are ubiquitous reports of seismic anisotropy below the '660' which are difficult to explain from a mineralogical point of view. In this study, we implement multigrain crystallography X-ray diffraction in the laser-heated diamond anvil cell in order to track microstructures induced by phase transitions at the pressure and temperature conditions of the discontinuity. Before the onset of transformation, garnet is isotropic with ringwoodite displaying a weak 001 texture. After the transformation, bridgmanite displays strong 001 transformation textures which we attribute to growth under stress. Davemaoite exhibits weak maxima in 101 and 111 orientations with ferropericlase displaying no texture. The results are used to model anisotropy in a subducting slab, with a prediction of no anisotropy above the '660' and up to 1.28% (0.08 km/s) shear wave splitting below the '660'. In addition, we predict V S V > V S H for horizontally traveling waves and near-vertical subduction and V S V < V S H in the case a slab impinging below the boundary layer. • Experimental study of transformation microstructures in polycrystalline pyrolite. • Multigrain crystallography to follow microstructures in-situ at relevant P and T. • Anisotropy observations below 660 may be due to growth of bridgmanite under stress. [ABSTRACT FROM AUTHOR]

Series of high-pressure x-ray diffraction patterns of iron and its high-pressure polymorphs were collected with 0.1-0.2-s exposure time utilizing a membrane diamond anvil cell (DAC) for compression at various loading and unloading rates to a maximum pressure of 70 GPa. Strain rates of 10-2s-1 at a maximum pressurization rate of 4.1 GPa/s were achieved in non-hydrostatic compression of hcp Fe. Linewidth analysis was used to retrieve strain and uniaxial stress of Fe as a function of pressure upon both compression and decompression. Analysis of the lattice parameters ratio c/a of hcp Fe indicates the presence of complex non-hydrostatic stress states, which developed as a function of strain rate, relaxation time, and various levels of hydrostaticity. Our results emphasize the importance of a controlled pressurization in DACs because the experimental loading rate strongly influences the stress state of the sample, particularly on decompression. Our time-resolved x-ray diffraction of the phase transition from bcc Fe to hcp Fe reveals residual grains of bcc Fe capable of surviving to very high pressures (>35 GPa) for a few minutes after the transition. [ABSTRACT FROM AUTHOR]

The compressional behaviour of (triclinic) pyrophyllite-1 Tc was investigated by means of in situ synchrotron single-crystal diffraction up to 6.2 GPa (at room temperature) using a diamond anvil cell. Its thermal behaviour was investigated by in situ synchrotron powder diffraction up to 923 K (at room pressure) with a furnace. No evidence of phase transition has been observed within the pressure range investigated. The α angle decreases whereas the β and γ angles increase with P, with the following linear trends: α( P) = α − 0.203(9)·Δ P, β( P) = β + 0.126(8)·Δ P, and γ( P) = γ + 0.109(5)·Δ P (angles in ° and P in GPa). P- V data fits with isothermal Murnaghan and third-order Birch-Murnaghan Equations of State yield: K = 47(3) GPa and K′ = 6.6(14) for the M-EoS fit, K = 47(4) GPa and K′ = 7.3(19) for a III-BM-EoS fit, with the following anisotropic compressional scheme: β: β: β = 1.06:1:4.00. The evolution of the 'Eulerian finite strain' versus 'normalized stress' leads to: Fe(0) = 47(3) GPa as intercept value and regression line slope with K′ = 7.1(18). A drastic and irreversible change of the thermal behaviour of pyrophyllite-1 Tc was observed at 700 < T < 850 K, likely ascribable to the first stage of the T-induced de-hydroxylation. Between 298 and 700 K, the α angle shows a slight decrease whereas the β and γ angles tend to be unaffected in response to the applied temperature; all the unit-cell edges show a monotonic increase. The axial and volume thermal expansion coefficients of pyrophyllite were modelled between 298 and 773 K following the equation α( T) = α(1 − 10 T), with α = 2.2(2) × 10 K [with V = 424.2(1) Å and α = 5.5(3) × 10 K] and thermal anisotropic scheme α: α: α = 1.20:1:2.72. By linear regression, we obtained: V( T)/ V = 1 + α· T = 1 + 3.1(2) × 10 ( T − T). The thermal behaviour of talc-1 Tc was investigated by in situ synchrotron powder diffraction up to 1,173 K (at room- P) with a furnace. At 423 K, the diffraction pattern was indexable with a monoclinic unit-cell but with a doubling of the c-axis (as expected for the 2 M-polytype). At T > 1,123 K, an irreversible transformation occurs, likely ascribable to the first stage of the T-induced de-hydroxylation. Between 423 and 1,123 K, the β angle decreases in response to the applied temperature; all the unit-cell edges show a monotonic increase. The volume expansion coefficient of talc was modelled between 423 and 1,123 K by the linear regression, yielding: V( T)/ V = 1 + α· T = 1 + 2.15(3) × 10 ( T − T). The comparative elastic analysis of pyrophyllite and talc, using the data obtained in this and in previous studies, shows that pyrophyllite is more compressible and more expandable than talc. [ABSTRACT FROM AUTHOR]

The crystal structure and vibrational spectra of the chlorpropamide have been studied by means of the X-ray diffraction and Raman spectroscopy at pressures up to 24.6 and 4.4 GPa, respectively. Two polymorphic phase transitions, between initial orthorhombic form-A and a monoclinic form-AI at P ∼ 1.2 GPa and, in additional, to another monoclinic form-AII at P ∼ 3.0 GPa, were observed. At pressures above 9.6 GPa, a transformation to the amorphous phase of chlorpropamide was revealed. The lattice parameters, unit cell volumes, and vibration modes as functions of pressure were obtained for the different polymorphic modifications of chlorpropamide. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:81-86, 2015 [ABSTRACT FROM AUTHOR]

We present time-resolved synchrotron x-ray diffraction measurements to study kinetics associated with the liquid-solid and solid-solid high-pressure phase transitions in Rr under dynamic loading in a dynamic-diamond anvil cell. The results show a strong compression-rate dependence of the solidification/melting process in liquid Kr. The analysis of the compression-rate dependent melting/solidification, using an Avrami equation with the parameter n = 1, indicates a spontaneous nucleation and one-dimensional growth mechanism. In contrast, the face-centered-cubic to metastable hexagonal close-packed transition in solid Kr occurs rapidly at ∼0.8 GPa near the melting line, which has negligible compression-rate dependence within the range of compression rates studied (0.004-13 GPa/s). [ABSTRACT FROM AUTHOR]

• Kurnakovite can be adopted as neutron-radiation absorber in concretes and tiles. • Its thermal and compressional behaviors have been studied by in situ XRD. • Dehydration-induced structural collapse occurs at T > 393 K. • At high- P , kurnakovite is stable under the conditions for any technical utilization. • Refined bulk α V and β V at ambient conditions: 5.18(1)·10−5 K−1 and 0.029(2) GPa−1. The thermal and compressional behaviors of kurnakovite, a potential B-rich aggregate in neutron radiation-shielding concretes, were studied by in situ single-crystal synchrotron X-ray diffraction (100–393 K, 0–13.36(5) GPa). Above 393 K, the crystal structure collapses in response to dehydration. The bulk thermal expansion coefficient is α V (298K) = 5.18(1)∙10−5 K−1. Volume compressional trend modelled with a Birch-Murnaghan equation of state yields a bulk modulus of K P0,T0 = 35(3) GPa. A phase transition occurs between 9.23(5) and 11.11(5) GPa, leading to a triclinic high- P polymorph (with triple unit-cell volume) and to an increase in coordination of one third of the trigonal-planar boron sites to a tetrahedral geometry. [ABSTRACT FROM AUTHOR]

Abstract: Ball-milled NaAlH4 was studied up to 15GPa in a diamond anvil cell (DAC) by X-ray diffraction using a synchrotron radiation source. Lattice parameters were determined from the X-ray diffraction data at various pressures up to 6.5GPa. Intensity of the powder diffraction patterns decreased with increasing pressure. Amorphisation started at a pressure of ∼6.5GPa and completed at 13.5GPa. Reversible phase transformation from amorphous phase to the tetragonal phase was observed. A fit to the pressure–volume data equation of state was obtained using the Birch–Murnaghan equation of state and the bulk modulus was found to be 52.16±0.9GPa which is twice higher than the unmilled NaAlH4. [Copyright &y& Elsevier]

We have synthesized the first hydrous sp 3 -carbonate by laser-heating Ba[CO 3 ], CO 2 and H 2 O in a diamond anvil cell at 40(3) GPa. The crystal structure of Ba[H 4 C 4 O 10 ][H 3 C 4 O 10 ][H 2 CO 3 ][HCO 3 ] was determined by synchrotron single crystal X-ray diffraction. The experiments were complemented by DFT-based calculations. This compound is the first example of a carbonate containing both trigonally-coordinated carbon in [CO 3 ] 2- -groups and tetrahedrally coordinated carbon in [CO 4 ] 4- -groups. The [CO 4 ] 4- -groups polymerize by corner-sharing to form pyramidal [C 4 O 10 ] 4- -groups, which can bind three or four hydrogen atoms. As the pyramidal [C 4 O 10 ] 4- -groups are a constituent of several anhydrous sp 3 -carbonates, we now expect that further high-pressure hydrous carbonates can be obtained.

Subducting sedimentary layer typically contains water and hydrated clay minerals. The stability of clay minerals under such hydrous subduction environment would therefore constraint the lithology and physical properties of the subducting slab interface. Here we show that pyrophyllite (Al 2 Si 4 O 10 (OH) 2 ), one of the representative clay minerals in the alumina-silica-water (Al 2 O 3 -SiO 2 -H 2 O, ASH) system, breakdowns to contain further hydrated minerals, gibbsite (Al(OH) 3 ) and diaspore (AlO(OH)), when subducts along a water-saturated cold subduction geotherm. Such a hydration breakdown occurs at a depth of ~135 km to uptake water by ~1.8 wt%. Subsequently, dehydration breakdown occurs at ~185 km depth to release back the same amount of water, after which the net crystalline water content is preserved down to ~660 km depth, delivering a net amount of ~5.0 wt% H 2 O in a phase assemblage containing δ-AlOOH and phase Egg (AlSiO 3 (OH)). Our results thus demonstrate the importance of subducting clays to account the delivery of ~22% of water down to the lower mantle., (© 2024. The Author(s).)

The inorganic pyrocarbonate salt Na 2 [C 2 O 5 ] crystallizes in the acentric, monoclinic space group P 2 1 with Z = 2. It contains monovalent alkali metal cations together with isolated pyrocarbonate anions. The [C 2 O 5 ] 2- -groups consist of two planar [CO 3 ] 2- -groups which are slightly tilted with respect to each other around the bridging oxygen atom. Na 2 [C 2 O 5 ] was synthesized in a laser-heated diamond anvil cell at 20(2) GPa by heating a mixture of Na 2 [CO 3 ] + CO 2 to ≈800(200) K. Its crystal structure was obtained by single crystal synchrotron X-ray diffraction and confirmed by density functional theory-based calculations in combination with Raman spectroscopy. Second harmonic generation measurements verified the acentric space group symmetry. The crystal structure is characterized by alternating layers of Na + -cations and [C 2 O 5 ] 2- -complex anions.

Giant impact-driven redox processes in the atmosphere and magma ocean played crucial roles in the evolution of Earth. However, because of the absence of rock records from that time, understanding these processes has proven challenging. Here, we present experimental results that simulate the giant impact-driven reactions between iron and volatiles (H 2 O and CO 2 ) using x-ray free electron laser (XFEL) as fast heat pump and structural probe. Under XFEL pump, iron is oxidized to wüstite (FeO), while volatiles are reduced to H 2 and CO. Furthermore, iron oxidation proceeds into formation of hydrides (γ-FeH x ) and siderite (FeCO 3 ), implying redox boundary near 300-km depth. Through quantitative analysis on reaction products, we estimate the volatile and FeO budgets in bulk silicate Earth, supporting the Theia hypothesis. Our findings shed light on the fast and short-lived process that led to reduced atmosphere, required for the emergence of prebiotic organic molecules in the early Earth.

An experimental platform for dynamic diamond anvil cell (dDAC) research has been developed at the High Energy Density (HED) Instrument at the European X-ray Free Electron Laser (European XFEL). Advantage was taken of the high repetition rate of the European XFEL (up to 4.5 MHz) to collect pulse-resolved MHz X-ray diffraction data from samples as they are dynamically compressed at intermediate strain rates (≤10 3  s -1 ), where up to 352 diffraction images can be collected from a single pulse train. The set-up employs piezo-driven dDACs capable of compressing samples in ≥340 µs, compatible with the maximum length of the pulse train (550 µs). Results from rapid compression experiments on a wide range of sample systems with different X-ray scattering powers are presented. A maximum compression rate of 87 TPa s -1 was observed during the fast compression of Au, while a strain rate of ∼1100 s -1 was achieved during the rapid compression of N 2 at 23 TPa s -1 ., (open access.)

When affected by impact, quartz (SiO 2 ) undergoes an abrupt transformation to glass lamellae, the planar deformation features (PDFs). This shock effect is the most reliable indicator of impacts and is decisive in identifying catastrophic collisions in the Earth´s record such as the Chicxulub impact. Despite the significance of PDFs, there is still no consensus how they form. Here, we present time-resolved in-situ synchroton X-ray diffraction data of single-crystal quartz rapidly compressed in a dynamic diamond anvil cell. These experiments provide evidence for the transformation of quartz at pressures above 15 GPa to lamellae of a metastable rosiaite (PbSb 2 O 6 )-type high-pressure phase with octahedrally coordinated silicon. This phase collapses during decompression to amorphous lamellae, which closely resemble PDFs in naturally shocked quartz. The identification of rosiaite-structured silica provides thus an explanation for lamellar amorphization of quartz. Furthermore, it suggests that the mixed phase region of the Hugoniot curve may be related to the progressive formation of rosiaite-structured silica., (© 2023. The Author(s).)

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.)

We have synthesized Pb[C 2 O 5 ], an inorganic pyrocarbonate salt, in a laser-heated diamond anvil cell (LH-DAC) at 30 GPa by heating a Pb[CO 3 ] + CO 2 mixture to ≈2000(200) K. Inorganic pyrocarbonates contain isolated [C 2 O 5 ] 2- groups without functional groups attached. The [C 2 O 5 ] 2- groups consist of two oxygen-sharing [CO 3 ] 3- groups. Pb[C 2 O 5 ] was characterized by synchrotron-based single-crystal structure refinement, Raman spectroscopy, and density functional theory calculations. Pb[C 2 O 5 ] is isostructural to Sr[C 2 O 5 ] and crystallizes in the monoclinic space group P 2 1 / c with Z = 4. The synthesis of Pb[C 2 O 5 ] demonstrates that, just like in other carbonates, cation substitution is possible and that therefore inorganic pyrocarbonates are a novel family of carbonates, in addition to the established sp 2 and sp 3 carbonates.

The synthesis of a novel type of carbonate, namely of the inorganic pyrocarbonate salt Sr[C 2 O 5 ], which contains isolated [C 2 O 5 ] 2- -groups, significantly extends the crystal chemistry of inorganic carbonates beyond the established sp 2 - and sp 3 -carbonates. We synthesized Sr[C 2 O 5 ] in a laser-heated diamond anvil cell by reacting Sr[CO 3 ] with CO 2 . By single crystal synchrotron diffraction, Raman spectroscopy, and density functional theory (DFT) calculations, we show that it is a pyrocarbonate salt. Sr[C 2 O 5 ] is the first member of a novel family of inorganic carbonates. We predict, based on DFT calculations, that further inorganic pyrocarbonates can be obtained and that these will be relevant to geoscience and may provide a better understanding of reactions converting CO 2 into useful inorganic compounds.

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.

We have synthesized the orthocarbonate Sr 3 [CO 4 ]O in a laser-heated diamond anvil cell at 20 and 30 GPa by heating to ≈3000 (300) K. Afterward, we recovered the orthocarbonate with [CO 4 ] 4- groups at ambient conditions. Single-crystal diffraction shows the presence of [CO 4 ] 4- groups, i.e., sp 3 -hybridized carbon tetrahedrally coordinated by covalently bound oxygen atoms. The [CO 4 ] 4- tetrahedra are located in a cage formed by corner-sharing OSr 6 octahedra, i.e., octahedra with oxygen as a central ion, forming an antiperovskite-type structure. At high pressures, the octahedra are nearly ideal and slightly rotated. The high-pressure phase is tetragonal ( I 4/ mcm ). Upon pressure release, there is a phase transition with a symmetry lowering to an orthorhombic phase ( Pnma ), where the octahedra tilt and deform slightly.

The European XFEL delivers up to 27000 intense (>10 12 photons) pulses per second, of ultrashort (≤50 fs) and transversely coherent X-ray radiation, at a maximum repetition rate of 4.5 MHz. Its unique X-ray beam parameters enable groundbreaking experiments in matter at extreme conditions at the High Energy Density (HED) scientific instrument. The performance of the HED instrument during its first two years of operation, its scientific remit, as well as ongoing installations towards full operation are presented. Scientific goals of HED include the investigation of extreme states of matter created by intense laser pulses, diamond anvil cells, or pulsed magnets, and ultrafast X-ray methods that allow their diagnosis using self-amplified spontaneous emission between 5 and 25 keV, coupled with X-ray monochromators and optional seeded beam operation. The HED instrument provides two target chambers, X-ray spectrometers for emission and scattering, X-ray detectors, and a timing tool to correct for residual timing jitter between laser and X-ray pulses., (open access.)

The ultrafast synthesis of ε-Fe 3 N 1+ x in a diamond-anvil cell (DAC) from Fe and N 2 under pressure was observed using serial exposures of an X-ray free electron laser (XFEL). When the sample at 5 GPa was irradiated by a pulse train separated by 443 ns, the estimated sample temperature at the delay time was above 1400 K, confirmed by in situ transformation of α- to γ-iron. Ultimately, the Fe and N 2 reacted uniformly throughout the beam path to form Fe 3 N 1.33 , as deduced from its established equation of state (EOS). We thus demonstrate that the activation energy provided by intense X-ray exposures in an XFEL can be coupled with the source time structure to enable exploration of the time-dependence of reactions under high-pressure conditions.

The blueschist to eclogite transition is one of the major geochemical-metamorphic processes typifying the subduction zone, which releases fluids triggering earthquakes and arc volcanism. Although glaucophane is an index hydrous mineral for the blueschist facies, its stability at mantle depths in diverse subduction regimes of contemporary and early Earth has not been experimentally determined. Here, we show that the maximum depth of glaucophane stability increases with decreasing thermal gradients of the subduction system. Along cold subduction geotherm, glaucophane remains stable down ca. 240 km depth, whereas it dehydrates and breaks down at as shallow as ca. 40 km depth under warm subduction geotherm or the Proterozoic tectonic setting. Our results imply that secular cooling of the Earth has extended the stability of glaucophane and consequently enabled the transportation of water into deeper interior of the Earth, suppressing arc magmatism, volcanism, and seismic activities along subduction zones.

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.)

High-pressure synthesis in diamond anvil cells can yield unique compounds with advanced properties, but often they are either unrecoverable at ambient conditions or produced in quantity insufficient for properties characterization. Here we report the synthesis of metallic, ultraincompressible (K 0  = 428(10) GPa), and very hard (nanoindentation hardness 36.7(8) GPa) rhenium nitride pernitride Re 2 (N 2 )(N) 2 . Unlike known transition metals pernitrides Re 2 (N 2 )(N) 2 contains both pernitride N 2 4- and discrete N 3- anions, which explains its exceptional properties. Re 2 (N 2 )(N) 2 can be obtained via a reaction between rhenium and nitrogen in a diamond anvil cell at pressures from 40 to 90 GPa and is recoverable at ambient conditions. We develop a route to scale up its synthesis through a reaction between rhenium and ammonium azide, NH 4 N 3 , in a large-volume press at 33 GPa. Although metallic bonding is typically seen incompatible with intrinsic hardness, Re 2 (N 2 )(N) 2 turned to be at a threshold for superhard materials.

A nitrogen-rich compound, ReN 8 ⋅x N 2 , was synthesized by a direct reaction between rhenium and nitrogen at high pressure and high temperature in a laser-heated diamond anvil cell. Single-crystal X-ray diffraction revealed that the crystal structure, which is based on the ReN 8 framework, has rectangular-shaped channels that accommodate nitrogen molecules. Thus, despite a very high synthesis pressure, exceeding 100 GPa, ReN 8 ⋅x N 2 is an inclusion compound. The amount of trapped nitrogen (x) depends on the synthesis conditions. The polydiazenediyl chains [-N=N-] ∞ that constitute the framework have not been previously observed in any compound. Ab initio calculations on ReN 8 ⋅x N 2 provide strong support for the experimental results and conclusions., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Due to their high technological and geological relevance, silicates are one of the most studied classes of inorganic compounds. Under ambient conditions, the silicon in silicates is almost exclusively coordinated by four oxygen atoms, while high-pressure treatment normally results in an increase in the coordination from four- to sixfold. Reported here is a high-pressure single-crystal X-ray diffraction study of danburite, CaB 2 Si 2 O 8 , the first compound showing a step-wise transition of Si coordination from tetrahedral to octahedral through a trigonal bipyramid. Along the compression, the Si 2 O 7 groups of danburite first transform into chains of vertice-sharing SiO 5 trigonal bipyramids (danburite-II) and later into chains of edge-sharing SiO 6 octahedra (danburite-III). It is suggested that the unusual formation of an SiO 5 configuration is a consequence of filling up the pentacoordinated voids in the distorted hexagonal close packing of danburite-II.

The doping effect of Sr(OH) 2 on the Mg(NH 2 ) 2 -2LiH system is investigated considering different amounts of added Sr(OH) 2 in the range of 0.05 to 0.2 mol. Experimental results show that both the thermodynamic and the kinetic properties of Mg(NH 2 ) 2 -2LiH are influenced by the presence of Sr(OH) 2 . The addition of 0.1 mol Sr(OH) 2 leads to a decrease in both the dehydrogenation onset and peak temperatures of ca. 70 and 13 °C, respectively, and an acceleration in the de/re-hydrogenation rates of one time at 150 °C compared to Mg(NH 2 ) 2 -2LiH alone. Based on differential scanning calorimetry (DSC) analysis, the overall reaction enthalpy of the 0.1 Sr(OH) 2 -doped sample is calculated to be 44 kJ per mol-H 2 and there are two absorption events occurring in the doped sample instead of one in the pristine sample. For the applied experimental conditions, according to the in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and Fourier Transform Infrared spectroscopy (FT-IR) analysis, the reaction mechanism has been finally defined: Sr(OH) 2 , Mg(NH 2 ) 2 and LiH react with each other to form SrO, MgO and LiNH 2 during ball milling. After heating, SrO interacts with Mg(NH 2 ) 2 producing MgO and Sr(NH 2 ) 2 . Then Mg(NH 2 ) 2 , LiNH 2 and Sr(NH 2 ) 2 react with LiH to produce Li 2 NH, SrNH, Li 2 Mg(NH) 2 and Li 2 Mg 2 (NH) 3 in traces. After re-hydrogenation, LiSrH 3 , LiH and LiNH 2 are formed along with amorphous Mg(NH 2 ) 2 . The reasons for the improved kinetics are: (a) during dehydrogenation, the in situ formation of SrNH appears to increase the interfacial contacts between Mg(NH 2 ) 2 and LiH and also weakens the N-H bond of Mg(NH 2 ) 2 ; (b) during absorption, the formation of LiSrH 3 at around 150 °C could be the key factor for improving the hydrogenation properties.

Titanium(III) phosphate, TiPO 4  , is a typical example of an oxyphosphorus compound containing covalent P-O bonds. Single-crystal X-ray diffraction studies of TiPO 4 reveal complex and unexpected structural and chemical behavior as a function of pressure at room temperature. A series of phase transitions lead to the high-pressure phase V, which is stable above 46 GPa and features an unusual oxygen coordination of the phosphorus atoms. TiPO 4 -V is the first inorganic phosphorus-containing compound that exhibits fivefold coordination with oxygen. Up to the highest studied pressure of 56 GPa, TiPO 4 -V coexists with TiPO 4 -IV, which is less dense and might be kinetically stabilized. Above a pressure of about 6 GPa, TiPO 4 -II is found to be an incommensurately modulated phase whereas a lock-in transition at about 7 GPa leads to TiPO 4 -III with a fourfold superstructure compared to the structure of TiPO 4 -I at ambient conditions. TiPO 4 -II and TiPO 4 -III are similar to the corresponding low-temperature incommensurate and commensurate magnetic phases and reflect the strong pressure dependence of the spin-Peierls interactions., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

One fascinating high-pressure behavior of tetrahedral glasses and melts is the local coordination change with increasing pressure, which provides a structural basis for understanding numerous anomalies in their high-pressure properties. Because the coordination change is often not retained upon decompression, studies must be conducted in situ. Previous in situ studies have revealed that the short-range order of tetrahedrally structured glasses and melts changes above a threshold pressure and gradually transforms to an octahedral form with further pressure increase. Here, we report a thermal effect associated with the coordination change at given pressures and show distinct thermal behaviors of GeO(2) glass in tetrahedral, octahedral, and their intermediate forms. An unusual thermally induced densification, as large as 16%, was observed on a GeO(2) glass at a pressure of 5.5 gigapascal (GPa), based on in situ density and x-ray diffraction measurements at simultaneously high pressures and high temperatures. The large thermal densification at high pressure was found to be associated with the 4- to 6-fold coordination increase. Experiments at other pressures show that the tetrahedral GeO(2) glass displayed small thermal densification at 3.3 GPa arising from the relaxation of intermediate range structure, whereas the octahedral glass at 12.3 GPa did not display any detectable thermal effects.