Gigapascal Research Articles

Cycloaddition of Butadiene with Perfluoroethylene: Prediction of a Periselectivity Switch under Pressure.

Defying the common Diels-Alder reactivity, the thermal cycloaddition between butadiene and tetrafluoroethylene (TFE) yields exclusively a [2 + 2] cycloadduct via a stepwise diradical mechanism. Here, we study the possibility of reverting to the normal [4 + 2] reactivity in this reaction under high pressure. DFT calculations using the eXtreme Pressure Polarizable Continuum Model (XP-PCM) suggest a more negative activation volume for the concerted [4 + 2] mechanism than the stepwise [2 + 2] mechanism and predict a switch in periselectivity at 1.4 gigapascal (GPa).

Investigating the steel–cement interface in high-temperature, high-pressure carbon dioxide environments

Abstract This study investigates the impact of high-temperature, high-pressure carbon dioxide on the steel-cement interface, crucial in engineering structures and carbon capture storage systems. Experiments conducted on N80 steel and ordinary portland cement in synthetic aquifer brine revealed that CO2 exposure significantly exacerbates steel corrosion and cement degradation. The corrosion current density of steel increased to 1.2 μA/cm2 after six months in CO2, compared to 0.3 μA/cm2 in unexposed samples. Cement samples showed a marked decline in mechanical properties, with hardness reducing from 1.25 GPa (giga-Pascal) in control samples to 0.65 GPa after six months. The steel—cement interface integrity also diminished, as evidenced by a decrease in acoustic impedance from 45.0 M-Rayl to 34.0 M-Rayl over six months. These results emphasize the need for advanced materials and strategies to enhance the durability and safety of structures in CO2-rich environments.

High-power laser beam shaping using a metasurface for shock excitation and focusing at the microscale.

Achieving high repeatability and efficiency in laser-induced strong shock wave excitation remains a significant technical challenge, as evidenced by the extensive efforts undertaken at large-scale national laboratories to optimize the compression of light element pellets. In this study, we propose and model a novel optical design for generating strong shocks at a tabletop scale. Our approach leverages the spatial and temporal shaping of multiple laser pulses to form concentric laser rings on condensed matter samples. Each laser ring initiates a two-dimensional focusing shock wave that overlaps and converges with preceding shock waves at a central point within the ring. We present preliminary experimental results for a single ring configuration. To enable high-power laser focusing at the micron scale, we demonstrate experimentally the feasibility of employing dielectric metasurfaces with exceptional damage threshold, experimentally determined to be 1.1 J/cm2, as replacements for conventional optics. These metasurfaces enable the creation of pristine, high-fluence laser rings essential for launching stable shock waves in materials. Herein, we showcase results obtained using a water sample, achieving shock pressures in the gigapascal (GPa) range. Our findings provide a promising pathway towards the application of laser-induced strong shock compression in condensed matter at the microscale.

Crystal Structure, Vibrational Spectra on Trivalent-Cation-Doped Rutile and Application in Optical Materials

Rutile is the most common TiO2 mineral with extensive application in the field of optical materials, and trivalent cations can significantly substitute Ti4+ with charge balanced by protonation. Several M3+-doped (M = Al, Ni, Co, Cr, Ga, Fe, and Mn) rutile samples were synthesized at 3 GPa (gigapascal) and 1273 K. The MO6-octahedral distortion model provides a reasonable explanation for the order of the M3+ concentrations. The total Cr3+ concentration was measured to be as high as 6.8 at % (atomic percentage) since the Cr3+O6 distortion is very close to that of Ti4+O6. This high Cr content significantly affects the Ti–O bonds and the lattice vibrations, and a quarter of the doped Al3+ and Cr3+ populations are identified in the interstitial sites. The M3+ effect on OH-stretching vibration was investigated by Fourier transform infrared (FTIR) spectra, which is useful for studying hydration mechanism in natural rutile samples with complex cationic substitutions. Besides, the doped-M3+ effect on the optical properties, including absorption, loss function, reflectivity, and refractive index, was studied by theoretical calculation. Incorporation of transition metal cations, especially Mn3+, significantly improves its optical performance in the visible light region, which is also confirmed by micro ultraviolet–visible–near infrared (UV–vis–NIR) spectra.

A dunite fragment in meteorite Northwest Africa (NWA) 11421: A piece of the Moon’s mantle

Abstract A centimeter-sized fragment of dunite, the first recognized fragment of Moon mantle material, has been discovered in the lunar highlands breccia meteorite Northwest Africa (NWA) 11421. The dunite consists of 95% olivine (Fo83), with low-Ca and high-Ca pyroxenes, plagioclase, and chrome spinel. Mineral compositions vary little across the clast and are consistent with chemical equilibration. Mineral thermobarometry implies that the dunite equilibrated at 980 ± 20 °C and 0.4 ± 0.1 gigapascal (GPa) pressure. The pressure at the base of the Moon’s crust (density 2550 kg/m3) is 0.14–0.18 GPa, so the dunite equilibrated well into the Moon’s upper mantle. Assuming a mantle density of 3400 kg/m3, the dunite equilibrated at a depth of 88 ± 22 km. Its temperature and depth of equilibration are consistent with the calculated present-day selenotherm (i.e., lunar geotherm). The dunite’s composition, calculated from mineral analyses and proportions, contains less Al, Ti, etc., than chondritic material, implying that it is of a differentiated mantle (including cumulates from a lunar magma ocean). The absence of phases containing P, Zr, etc., suggests minimal involvement of a KREEP component, and the low proportion of Ti suggests minimal interaction with late melt fractionates from a lunar magma ocean. The Mg/Fe ratio of the dunite (Fo83) is significantly lower than models of an overturned unmixed mantle would suggest, but is consistent with estimates of the bulk composition of the Moon’s mantle.

Rhenium carbides phase diagram under pressure and explaining why WC-type ReC does not exist

The stability of W–C compounds (WC)-type ReC has been controversial for many years. Here, based on ab initio algorithm, we systematically searched for stable structures in the rhenium–carbon (Re–C) system at 0–300 gigapascal (GPa) pressure and analyzed the phase diagram within the pressure range. Only P63/mmc-Re2C, C2/m-Re3C, P21/m-Re4C, and C2/m-Re5C2 phases are found to be stable under 0–300 GPa, while WC-type ReC has high enthalpy and does not appear in the phase diagram. We also discussed the stability of WC-type ReC. Among these structures, C2/m-Re3C, P21/m-Re4C, and C2/m-Re5C2 are hitherto unknown structures, which could maintain dynamic and mechanical stability under ambient pressure. In addition, through the analysis of the structural and mechanical properties, P63/mmc-Re2C is the hardest metal among them with 31.5 GPa Vickers hardness at 0 GPa, and the metastable P6¯m2-Re5C3 has the second-highest hardness (29.3 GPa), both of which exceed the hardness of TiN (18.7 GPa), the commercial material used for cutting tools. The study of Re–C compounds with high hardness provides theoretical guidance for further experimental research.

Ultrasound elasticity of diamond at gigapascal pressures

Diamond is the hardest known material in nature and features a wide spectrum of industrial and scientific applications. The key to diamond's outstanding properties is its elasticity, which is associated with its exceptional hardness, shear strength, and incompressibility. Despite many theoretical works, direct measurements of elastic properties are limited to only ∼1.4 kilobar (kb) pressure. Here, we report ultrasonic interferometry measurements of elasticity of void-free diamond powder in a multianvil press from 1 atmosphere up to 12.1 gigapascal (GPa). We obtained high-accuracy bulk modulus of diamond as K0 = 439.2(9) GPa, K0' = 3.6(1), and shear modulus as G0 = 533(3) GPa, G0' = 2.3(3), which are consistent with our first-principles simulation. In contrast to the previous experiment of isothermal equation of state, the K0' obtained in this work is evidently greater, indicating that the diamond is not fully described by the "n-m" Mie-Grüneisen model. The structural and elastic properties measured in this work may provide a robust primary pressure scale in extensive pressure ranges.

High hardness metal compounds: Prediction of Re3C under pressure

High-hardness metal compounds have huge potential applications in multifunctional devices used under extreme conditions. Here, an ab initio evolutionary algorithm was used to systematically search for structures in the Re3C system with high hardness and metallicity under the pressure of 0–300 gigapascal (GPa). We discovered a structure (namely, C2/m) with the lowest enthalpy at 154 GPa and two metastable phases (namely, P63/mmc and C2/m-α), which could maintain thermodynamic and mechanical stability at zero pressure, and they could be quenched to ambient conditions. More importantly, the hardness of the metal compounds (21.4 GPa for C2/m, 25.2 GPa for P63/mmc) exceeds that of TiN (18.7 GPa), the material for commercial machine tools. In addition, our analysis shows that the coexistence of Re–C bond and Re–Re bond with strong coupling, and avoiding the antibonding state of 5d-electron of Re–Re bond near the Fermi level, could be the reasons why the structure has high hardness and metal properties at the same time.

Pressure Gradient Squeezing Hydrogen out of MnOOH: Thermodynamics and Electrochemistry.

Pressure of gigapascal (GPa) is a robust force for driving phase transitions and chemical reactions with negative volume change and is intensely used for promoting combination/addition reactions. Here, we find that the pressure gradient between the high-pressure region and the ambient-pressure environment in a diamond anvil cell is an even stronger force to drive decomposition/elimination reactions. A pressure difference of tens of GPa can "push" hydrogen out from its compounds in the high-pressure region to the environment. More importantly, in transition metal hydroxides such as MnOOH, the protons and electrons of hydrogen can even be separated via different conductors, pushed out by the high pressure, and recombine outside under ambient conditions, producing continuous current. A pressure-gradient-driven battery is hence proposed. Our investigation demonstrated that a pressure gradient is a special and powerful force to drive decomposition and electrochemical reactions.

Giant shape- and size-dependent compressive strength of molybdenum nano- and microparticles

The ability to process metallic samples at the sub-micrometer scale raised the strength limits of pure metals to the Giga Pascal (GPa) range. Here, we fabricated Mo nanoparticles with a giant compressive strength surpassing the previous strength records of metallic materials. Round and faceted particles were produced by manipulating the annealing atmosphere during two-stage solid-state dewetting of Mo thin films deposited on sapphire. The round particle underwent a huge elastic deformation before yielding abruptly. Using finite element analysis, we found that the resolved shear stress on a {112}〈110〉 slip system beneath the punch reaches an enormous value of 20±1 GPa at yield, regardless of particle size. The faceted nanoparticles, contrarily, followed a “smaller is stronger” rule, with uniaxial compressive strength of up to 46 GPa for the smallest nanoparticles. Molecular dynamics simulations indicated that the size effect diminishes with increasing roundness of the particle edges. This work demonstrates how shape and size of particles can be manipulated to achieve giant strength.

Crystal and Magnetic Structures of Double Hexagonal Close-Packed Iron Deuteride

Neutron powder diffraction profiles were collected for iron deuteride (FeDx) while the temperature decreased from 1023 to 300 K for a pressure range of 4–6 gigapascal (GPa). The ε′ deuteride with a double hexagonal close-packed (dhcp) structure, which coexisted with other stable or metastable deutrides at each temperature and pressure condition, formed solid solutions with a composition of FeD0.68(1) at 673 K and 6.1 GPa and FeD0.74(1) at 603 K and 4.8 GPa. Upon stepwise cooling to 300 K, the D-content x increased to a stoichiometric value of 1.0 to form monodeuteride FeD1.0. In the dhcp FeD1.0 at 300 K and 4.2 GPa, dissolved D atoms fully occupied the octahedral interstitial sites, slightly displaced from the octahedral centers in the dhcp metal lattice, and the dhcp sequence of close-packed Fe planes contained hcp-stacking faults at 12%. Magnetic moments with 2.11 ± 0.06 μB/Fe-atom aligned ferromagnetically in parallel on the Fe planes.

Giant Size- and Shape-Dependent Uniaxial Compressive Strength of Molybdenum Nano- and Microparticles

The ability to process metallic samples at the sub-micrometer scale raised the strength limits of pure metals to the Giga Pascal (GPa) range. Here, we fabricated Mo nanoparticles with a giant compressive strength surpassing the previous strength records of metallic materials. Round and faceted particles were produced by manipulating the annealing atmosphere during two-stage solid-state dewetting of Mo thin films deposited on sapphire. The round particle underwent a huge elastic deformation before yielding abruptly. Using finite elements analysis, we found that the resolved elastic shear stress on a {112} slip system beneath the punch reaches an enormous value of 20±1 GPa regardless of particle size. The faceted nanoparticles, contrarily, followed a smaller is stronger rule, with uniaxial compressive strength of up to 46 GPa for the smallest nanoparticles. Molecular dynamics simulations indicated that the size effect diminishes with increasing roundness of the particle edges. This work demonstrates how shape and size of particles can be manipulated to achieve giant strength.

TAVOLA PERIODICA SOTTO PRESSIONE: UNA PERIODICITA' DIVERSA ED UNA CHIMICA ESOTICA

Our general and operative notion of chemistry, that enabling us to describe and interpret the structural, bonding and reactivity properties of the various compounds, is essentially rooted in the periodicity of properties of their constituting elements. Periodicity drove the path towards the proposition of the periodic table of elements and its rationalization thanks to the gradually acquired knowledge on the atomic electronic structure. Atomic radii periodicity mirrors the periodicity of the electronic configurations of the atoms’ outermost shell. The changes in atomic radii differentiate the chemical properties, hence the structures and properties of the elemental solids and of their compounds. Yet, under an external pressure, such a fully rationalized scenario may drastically change. When an atom is compressed, its average electron density increases and its outermost electronic shell is the easiest one to compress. At 100 Giga Pascal (GPa), that is at 106 atmospheres, the change of the atomic radius along a period of the Periodic Table becomes much less evident and at 1000 GPa our classical notion of periodicity is completely lost. Under pressure, the energy due to the compression work made on a system adds up to its internal energy. With such an energy gain the system may reach regions of the potential energy surface which would not be otherwise accessible. The chemical bond nature may change, even radically, and new structures and bonding patterns, characterized by totally unexpected properties, become energetically stable and possible. For instance, sodium, which is a silvery-white, highly reactive metal, becomes a fully transparent insulator, while boron is turned into a partially ionic solid elemental phase because charge transfer takes place between differently clustered groups of boron atoms. The incredible chemical inertness of helium finally falls as it forms a stable compound with sodium, Na2He. Under a suitable pressure, compounds with unusual stoichiometry (Na3Cl2, Na2Cl, Na3Cl, NaCl3, NaCl7) may be observed, despite their formula would be immediately rejected if proposed by a student at any high-school or university exam, or new carbon allotropes may appear or the aromatic character of benzene may vanish. This new chemistry is usually predicted through ab-initio quantum mechanical methods and interpreted and rationalized with the most modern chemical bonding approaches. However, compounds anticipated in silico have then be reproduced experimentally in many cases, by using diamond anvil cells to synthesize them and a variety of in situ instrumental techniques to characterize them properly.

High resolution wide range pressure sensor using hexagonal ring and micromachined cantilever tips on 2D silicon photonic crystal

Abstract Design of a pressure sensor workable from megapascal (MPa) to gigapascal (GPa) pressure range is proposed on a two dimensional triangular/hexagonal lattice silicon (Si) photonic crystal (PhC) arrangement. In order to ensure high resolution sensing over this wide pressure range, a hexagonal shaped ring of hexagonal unit cells and two micromachined silicon cantilever tips are considered on the photonic crystal arrangement. The concept of using micromachined cantilever tip in a PhC arrangement for optical sensing of pressure is novel. Moreover, use of hexagonal ring with hexagonal unit cells make the structure more sensitivity than other types of ring arrangement. It is shown that the two silicon cantilever tips can be used to detect applied pressure from 1 MPa to 10 MPa with resolution of 1 MPa and 10 MPa to 100 MPa with a resolution of 10 MPa, respectively. Detection of applied pressure from 20 MPa to 10 GPa with the resolution of 20 MPa can be done using the hexagonal ring of hexagonal unit cells. The entire design is done using the MPB (MIT Photonic Bands) and MEEP (MIT Electromagnetic Equation Propagation) simulators freely available from MIT, USA.

Bacterial survival following shock compression in the GigaPascal range

The possibility that life can exist within previously unconsidered habitats is causing us to expand our understanding of potential planetary biospheres. Significant populations of living organisms have been identified at depths extending up to several km below the Earth's surface; whereas laboratory experiments have shown that microbial species can survive following exposure to GigaPascal (GPa) pressures. Understanding the degree to which simple organisms such as microbes survive such extreme pressurization under static compression conditions is being actively investigated. The survival of bacteria under dynamic shock compression is also of interest. Such studies are being partly driven to test the hypothesis of potential transport of biological organisms between planetary systems. Shock compression is also of interest for the potential modification and sterilization of foodstuffs and agricultural products. Here we report the survival of Shewanella oneidensis bacteria exposed to dynamic (shock) compression. The samples examined included: (a) a “wild type” (WT) strain and (b) a “pressure adapted” (PA) population obtained by culturing survivors from static compression experiments to 750MPa. Following exposure to peak shock pressures of 1.5 and 2.5GPa the proportion of survivors was established as the number of colony forming units (CFU) present after recovery to ambient conditions. The data were compared with previous results in which the same bacterial samples were exposed to static pressurization to the same pressures, for 15 minutes each. The results indicate that shock compression leads to survival of a significantly greater proportion of both WT and PA organisms. The significantly shorter duration of the pressure pulse during the shock experiments (2–3 µs) likely contributes to the increased survival of the microbial species. One reason for this can involve the crossover from deformable to rigid solid-like mechanical relaxational behavior that occurs for bacterial cell walls on the order of seconds in the time-dependent strain rate.

Neutron diffraction as a probe of liquid and glass structures under extreme conditions

Neutrons provide a unique tool for probing the structure of liquid and glassy materials, and deliver information that cannot be obtained from other experimental techniques. Advances in neutron diffraction instrumentation and measurement protocols now make it possible to measure the structure of these disordered materials under extremes of high temperatures or high pressures. Here, we consider the use of aerodynamic levitation with laser heating to explore the structure of glass-forming oxide melts at high temperatures, and the use of a Paris Edinburgh press to investigate the mechanisms of density-driven network collapse for glassy materials in the gigapascal (GPa) pressure regime.

High-sensitivity NMR beyond 200,000 atmospheres of pressure

Pressure-induced changes in the chemical or electronic structure of solids require pressures well into the Giga-Pascal (GPa) range due to the strong bonding. Anvil cell designs can reach such pressures, but their small and mostly inaccessible sample chamber has severely hampered NMR experiments in the past. With a new cell design that has a radio frequency (RF) micro-coil in the high pressure chamber, NMR experiments beyond 20 Giga-Pascal are reported for the first time. 1H NMR of water shows sensitivity and resolution obtained with the cells, and 63Cu NMR on a cuprate superconductor (YBa2Cu3O7-δ) demonstrates that single-crystals can be investigated, as well. 115In NMR of the ternary chalcogenide AgInTe2 discovers an insulator-metal transition with shift and relaxation measurements. The pressure cells can be mounted easily on standard NMR probes that fit commercial wide-bore magnets with regular cryostats for field- and temperature-dependent measurements ready for many applications in physics and chemistry.

Hypervelocity Pressure Fields Driven by Cylindrical Converging Shock Used for Accelerating Dense Metal Particles

The Cylindrical Converging Shock Tube is a novel explosion technology used to drive a shock or detonation wave through a core material at high velocity. The system contains an inner core and outer explosive annulus separated with an inner metal liner. Axial detonation of the annular explosive transmits a centrally converging shock in the form of a Mach stem into the core. With a slight modification to a Cylindrical Converging Shock Tube, a super compression detonation shock tube can be created which can provide a reactive core velocity of over 10km/s by overdriving the annular explosive. An internal core pressure of several hundred gigapascal (GPa) can be produced depending on the item's geometry and core material properties. The study first examines the pressure fields in an inert PMMA core and then repeats the simulation for a reactive multiphase material of HMX/Al-W to identify the dynamics of an inert particle laden core. This study uses a Eulerian-to–Lagrangian conversion method to describe the particle dynamics occurring within the core.

High-sensitivity nuclear magnetic resonance at Giga-Pascal pressures: a new tool for probing electronic and chemical properties of condensed matter under extreme conditions.

Nuclear Magnetic Resonance (NMR) is one of the most important techniques for the study of condensed matter systems, their chemical structure, and their electronic properties. The application of high pressure enables one to synthesize new materials, but the response of known materials to high pressure is a very useful tool for studying their electronic structure and developing theories. For example, high-pressure synthesis might be at the origin of life; and understanding the behavior of small molecules under extreme pressure will tell us more about fundamental processes in our universe. It is no wonder that there has always been great interest in having NMR available at high pressures. Unfortunately, the desired pressures are often well into the Giga-Pascal (GPa) range and require special anvil cell devices where only very small, secluded volumes are available. This has restricted the use of NMR almost entirely in the past, and only recently, a new approach to high-sensitivity GPa NMR, which has a resonating micro-coil inside the sample chamber, was put forward. This approach enables us to achieve high sensitivity with experiments that bring the power of NMR to Giga-Pascal pressure condensed matter research. First applications, the detection of a topological electronic transition in ordinary aluminum metal and the closing of the pseudo-gap in high-temperature superconductivity, show the power of such an approach. Meanwhile, the range of achievable pressures was increased tremendously with a new generation of anvil cells (up to 10.1 GPa), that fit standard-bore NMR magnets. This approach might become a new, important tool for the investigation of many condensed matter systems, in chemistry, geochemistry, and in physics, since we can now watch structural changes with the eyes of a very versatile probe.

Formation of the –N(NO)N(NO)– polymer at high pressure and stabilization at ambient conditions

A number of exotic structures have been formed through high-pressure chemistry, but applications have been hindered by difficulties in recovering the high-pressure phase to ambient conditions (i.e., one atmosphere and 300 K). Here we use dispersion-corrected density functional theory [PBE-ulg (Perdew-Burke-Ernzerhof flavor of DFT with the universal low gradient correction for long range London dispersion)] to predict that above 60 gigapascal (GPa) the most stable form of N2O (the laughing gas in its molecular form) is a one-dimensional polymer with an all-nitrogen backbone analogous to cis-polyacetylene in which alternate N are bonded (ionic covalent) to O. The analogous trans-polymer is only 0.03∼0.10 eV/molecular unit less stable. Upon relaxation to ambient conditions, both polymers relax below 14 GPa to the same stable nonplanar trans-polymer. The predicted phonon spectrum and dissociation kinetics validates the stability of this trans-poly-NNO at ambient conditions, which has potential applications as a type of conducting nonlinear optical polymer with all-nitrogen chains and as a high-energy oxidizer for rocket propulsion. This work illustrates in silico materials discovery particularly in the realm of extreme conditions (very high pressure or temperature).