High Pressure Regime Research Articles

Proteins in Wonderland: The Magical World of Pressure.

Simple SummaryUnlike temperature, pH or chemical reagent, the effect of hydrostatic pressure on proteins is unique in that it controls selectively the equilibrium populations among different conformational states, without practically affecting each of their structures. Because of this unique effect of hydrostatic pressure on proteins, the application of pressure can easily manipulate the population distribution among different conformational states of a protein to a considerable extent at our will, creating what may be called “the magical world of pressure” or “the wonderland for proteins”. In this paper, we have succssfully utilized the magical world of pressure in bringing the amyloid fibrils F of wild-type hen lysozyme into the unfolded monomers U and then, upon returning to the Anfinsen regime, back into its original, natively folded state N.Admitting the “Native”, “Unfolded” and “Fibril” states as the three basic generic states of proteins in nature, each of which is characterized with its partial molar volume, here we predict that the interconversion among these generic states N, U, F may be performed simply by making a temporal excursion into the so called “the high-pressure regime”, created artificially by putting the system under sufficiently high hydrostatic pressure, where we convert N to U and F to U, and then back to “the low-pressure regime” (the “Anfinsen regime”), where we convert U back to N (U→N). Provided that the solution conditions (temperature, pH, etc.) remain largely the same, the idea provides a general method for choosing N, U, or F of a protein, to a great extent at will, assisted by the proper use of the external perturbation pressure. A successful experiment is demonstrated for the case of hen lysozyme, for which the amyloid fibril state F prepared at 1 bar is turned almost fully back into its original native state N at 1 bar by going through the “the high-pressure regime”. The outstanding simplicity and effectiveness of pressure in controlling the conformational state of a protein are expected to have a wide variety of applications both in basic and applied bioscience in the future.

Pressure-induced superconductivity and structure phase transition in Pt2HgSe3

Recently monolayer jacutingaite (Pt2HgSe3), a naturally occurring exfoliable mineral, discovered in Brazil in 2008, has been theoretically predicted as a candidate quantum spin Hall system with a 0.5 eV band gap, while the bulk form is one of only a few known dual-topological insulators that may host different surface states protected by symmetries. In this work, we systematically investigate both structure and electronic evolution of bulk Pt2HgSe3 under high pressure up to 96 GPa. The nontrivial topology is theoretically stable, and persists up to the structural phase transition observed in the high-pressure regime. Interestingly, we found that this phase transition is accompanied by the appearance of superconductivity at around 55 GPa and the critical transition temperature Tc increases with applied pressure. Our results demonstrate that Pt2HgSe3 with nontrivial topology of electronic states displays a ground state upon compression and raises potentials in application to the next-generation spintronic devices.

Electronegativity under Confinement.

The electronegativity concept was first formulated by Pauling in the first half of the 20th century to explain quantitatively the properties of chemical bonds between different types of atoms. Today, it is widely known that, in high-pressure regimes, the reactivity properties of atoms can change, and, thus, the bond patterns in molecules and solids are affected. In this work, we studied the effects of high pressure modeled by a confining potential on different definitions of electronegativity and, additionally, tested the accuracy of first-order perturbation theory in the context of density functional theory for confined atoms of the second row at the Hartree–Fock level. As expected, the electronegativity of atoms at high confinement is very different than that of their free counterparts since it depends on the electronic configuration of the atom, and, thus, its periodicity is modified at higher pressures.

On-site in situ high-pressure ultrafast pump-probe spectroscopy instrument.

We conceive and construct an on-site in situ high-pressure time-resolved ultrafast optical spectroscopy instrument that facilitates ultrafast pump-probe dynamics measurements under high pressure conditions. We integrate an ultrafast pump-probe spectroscopy system with a diamond anvil cell (DAC) system. Significantly, both the DAC and the sample are fixed within the light path without motion and rotation throughout the whole ultrafast spectroscopy experiment, including tuning and calibrating the pressure. This instrument thus avoids introducing artifacts due to sample motion or rotation, enabling precision high-pressure ultrafast pump-probe dynamics investigations. As a demonstrating example, we compare the effect of on-site in situ conditions with off-site in situ conditions on the ultrafast dynamics of Sr2IrO4 under 0-44.5GPa high pressure. Our data and analysis show that conventional possible artifacts are greatly reduced by using the on-site in situ layout. Our work helps the high-pressure ultrafast science investigation develop into a promising new area, which enables the exploration of nonequilibrium excited quantum states in the high-pressure regime.

Effect of van Hove singularity on the isotope effect and critical temperature of H3S hydride superconductor as a function of pressure

We have performed density functional calculations in conjunction with the linearized Migdal-Eliashberg equations and the functional derivative approach, which takes into account the energy-range dependence of the density of states at the Fermi level (N(ϵ) variable on the scale of phonon energy), to determine the evolution of the critical temperature (Tc) and the isotope effect coefficient (α) of H3S as a function of pressure on its lm3̄m crystal-structure range (from 162 to 250 GPa). Such approach, in comparison with N(ϵ) = N(0) = const., improves the agreement of Tc with available experiments on the whole range of studied pressure. Considering for α two main contributions: one positive coming from the electron-phonon (el-ph) and the other negative from the electron-electron interaction (el-el), we obtained a monotonic decrement as a function of pressure, independent of applied scheme (N(ϵ) or N(0)). However, when N(ϵ) is taken into account, an important renormalization occurs on both contributions, el-ph and el-el, improving the agreement with experimental data, specially for the high-pressure regime. The observed evolution of Tc and α as a function of pressure indicates, thus, the crucial role of the energy-dependence on N(ϵ) for the proper analysis and description of the superconducting state on high-Tc metal hydrides as H3S, by considering the role of its van Hove singularities.

Enhancing permeability and porosity of ceramic shells for investment casting through pre-wetting

In this study, a method known as pre-wetting is applied between the multilayer ceramic investment casting shells to enhance porosity and permeability while sustaining flexural strength. Pre-wetting consists predominately of an aqueous silica binder that improves inter-coat bonding in complex areas. Porosity is developed where the pre-wetting is applied due to the evaporation of the aqueous phase. Results indicate that as porosity increases, both green and fired flexural strength reduce on average by 8.7 - 15.6 % and 18.7 - 28.5 %, respectively, whereas hot strength is increased by 20 - 25 %. Permeability increased by a factor of two when pre-wetting was applied between intermediate coatings and displayed a stepwise increase in intrusion volume in the high-pressure regime through mercury intrusion porosimetry. X-ray microtomography coupled with pore network modelling provided a validation of the increase in the permeability constant. Gas adsorption methods revealed the presence of micropores through the alpha-s method when bilayers of pre-wetting solution were applied.

Kirigami-inspired dual-parameter tactile sensor with ultrahigh sensitivity, multimodal and strain-insensitive features

Soft sensors with strain-insensitive and multimodal features are intriguing due to their high practical relevance. However, incorporating these functionalities into sensors made of soft materials has been challenging. Herein, a Kirigami-inspired dual-parameter tactile sensor was developed with strain-insensitive and multimodal features. The tactile sensor uses piezoresistive and capacitive transduction modes allowing simultaneous detection of dynamic and static tensile strains, proximity and normal pressures. The convenient structural design enables ultrahigh piezoresistive sensitivity ∼23 000 kPa−1 in its resistivity-switching threshold region (in high pressure regimes >50 kPa). It achieves a linear capacitive gauge factor of ∼14.48 for uniaxial elongation up to 80% strain and can accurately measure proximity (⩾0.01 pF mm−1) of objects within distances up to 100 mm. The ultrahigh sensitivity in high pressure regimes allows force adjustable lower limit of detection and sensitivity of the sensor by pre-stress enabling real-time measurement of arterial pulsation. The findings of this work support the design of soft sensors for touch recognition applications in the automotive industry, soft robots or self-adjusting grippers requiring a sense of touch and multimodal and strain-insensitive features.

High-pressure effects on superconducting properties and crystal structure of Bi-based layered superconductor La2O2Bi3Ag0.6Sn0.4S6

The effects of pressure on the superconducting properties of a Bi-based layered superconductor La2O2Bi3Ag0.6Sn0.4S6, which possesses a four-layer-type conducting layer, have been studied through the electrical resistance and magnetic susceptibility measurements. The crystal structure under pressure was examined using synchrotron x-ray diffraction at SPring-8. In the low-pressure regime, bulk superconductivity with a transition temperature T c of ∼4.5 K was induced by pressure, which was achieved by in-plane chemical pressure effect owing to the compression of the tetragonal structure. In the high-pressure regime above 6.4 GPa, a structural symmetry lowering was observed, and superconducting transitions with a T c ∼ 8 K were observed. Our results suggest the possible commonality on the factor essential for T c in Bi-based superconductors with two-layer-type and four-layer-type conducting layers.

Superconductivity and strong anharmonicity in novel Nb–S phases

In this work we explore the phase diagram of the binary Nb–S system from ambient pressures up to 250 GPa using ab initio evolutionary crystal structure prediction. We find several new stable compositions and phases, especially in the high-pressure regime, and investigate their electronic, vibrational, and superconducting properties. Our calculations show that all materials, besides the low-pressure phases of pure sulfur, are metals with low electron–phonon (ep) coupling strengths and critical superconducting temperatures below 15 K. Furthermore, we investigate the effects of phonon anharmonicity on lattice dynamics, ep interactions, and superconductivity for the novel high-pressure phase of Nb2S, demonstrating that the inclusion of anharmonicity stabilizes the lattice and enhances the ep interaction.

CO2 and H2 adsorption on 3D nitrogen-doped porous graphene: Experimental and theoretical studies

Carbon dioxide (CO2) and hydrogen (H2) adsorptions were investigated on 3D nitrogen-doped porous graphene (GO-PAA) produced by chemical activation of graphene oxide impregnated with polyallylamine (PAA). GO-PAA characterizations by Raman and X-ray photoelectron spectroscopies, thermogravimetric analysis, N2 adsorption-desorption isotherms, scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed that GO-PAA shows excellent thermal stability, decomposing at temperatures higher than 450 °C, specific surface area of 1155 m2 g−1, with pyrrolic, pyridinic and graphitic nitrogen atoms homogeneously dispersed throughout its 3D porous structure. The mesoporous nature of GO-PAA and the nitrogen doping level of 7.5 wt% resulted in remarkable H2 (1.3 wt%) and CO2 (20 mmol g−1) adsorption capacities at room temperature (RT, 25 °C) under high-pressure regime (40 bar). This H2 adsorption capacity at RT is among the highest values reported in the open literature. The role of the nitrogen atoms on the gas adsorption properties was investigated by combining experimental data, such as isosteric heat and Diffuse Reflectance Infrared Fourier Transform spectroscopy, with theoretical calculations using Density-Functional Theory. Inclusion of nitrogen atoms in the graphene structure reduces the energies of the Frontier Molecular Orbitals, facilitating polarization and increasing the interaction energy.

Dynamic Strength of Copper at High Pressures Using Pressure Shear Plate Experiments

Measurement of strength at high pressures is critical to understanding the behavior of materials subjected to extreme loading conditions. Recent developments have extended the pressure shear plate impact (PSPI) technique to the high-pressure regime. Such experiments provide a unique opportunity to extract the complete stress–strain behavior of materials at relatively high pressures. The modified technique includes a new fiber-optic heterodyne transverse velocity interferometer system and new analysis methods to account for the inelastic response of the anvil plates. In this study, PSPI experiments are conducted on oxygen-free high conductivity (OFHC) copper at pressures ranging from 10 to 43 GPa and at strain rates of ~ 105 s−1. Complete stress–strain curves of copper are obtained using a hybrid methodology that relies on numerical simulations and particle velocity records gathered in these experiments. Experiments are conducted at similar pressures and strain rates using two types of anvils that undergo different levels of plastic strains: tool steel and tungsten carbide, to check the robustness of the hybrid method. The behavior of copper at these high pressures and strain rates is compared with previous literature data, and the effect of pressure and strain rate on the strength behavior of copper are discussed. It was observed that the rate of change in yield strength with pressure was 2.5 times the rate of change of shear modulus with pressure. The strength models that predict the response of copper at these extreme conditions are also examined and validated.

A combined synchrotron diffraction and first-principles investigation on structural properties of Co(OH)2under pressure up to 7 GPa

An H–H repulsion induced structural anomaly in Co(OH)2 at pressure around 2.5 GPa is reported using systematic synchrotron X-ray powder diffraction and density functional theory (DFT) based first-principles calculations. The diffraction pattern evidences anomalous pressure dependence of Bragg peaks (003) and (013) compared to others indicating a much stronger change in the hydrogen sublattice with pressure. Analysis of the lattice parameters reveals a subtle but clear change in the trend of the out-of-plane to in-plane lattice constants' ratio above 2.5 GPa. Two independent pressure runs using two different pressure transmitting media yielded similar results, thus proving the observations to be independent of the minor variations in the quasi-hydrostatic conditions during the pressure run. DFT calculations were performed on an extended unit cell of Co(OH)2 which enables the description of hydrogen in either ordered or disordered state. Calculations showed that only the hydrogen disordered structure is energetically favourable at high pressures. We attribute the anomalous behaviour of the (003) and (013) Bragg peaks above 2.5 GPa to the charge delocalization along hydrogen sublattice coming due to the hydrogen ordered-disordered transition, in agreement with DFT results showing the H disordered state to be energetically more favourable at higher pressure. A second-order Brich-Murnaghan equation of state (EoS) can well describe the low- and high-pressure regime separately with a 20% higher bulk modulus of the latter, further supporting the subtle transition around 2.5 GPa. Present results also complement the previous Raman spectroscopic study on Co(OH)2 which reported anomalous behaviour in the (2) mode around 2.5 GPa.

Pressure-induced isostructural electronic topological transitions in 2H-MoTe2: x-ray diffraction and first-principles study

Synchrotron x-ray diffraction measurements on powder 2H-MoTe2 (P63/mmc) up to ∼46 GPa have been performed along with first-principles based density functional theoretical analysis to probe the isostructural transition in low pressure regime and two electronic topological transitions (ETT) of Lifshitz-type in high pressure regime. The low pressure isostructural transition at ∼7 GPa is associated with the lattice parameter ratio c/a anomaly and the change in the compressibility of individual layers. The pressure dependence of the volume by linearizing the Birch–Murnaghan equation of state as a function of Eulerian strain shows a clear change of the bulk modulus at the ETT pressure of ∼20 GPa. The minimum of c/a ratio around 32 GPa is associated with the change in topology of electron pockets marked as second ETT of Lifshitz-type. We do not observe any structural transition up to the maximum applied pressure of ∼46 GPa under quasi-hydrostatic condition.

Pressure-Shear Plate Impact Experiments at High Pressures

The pressure shear plate impact (PSPI) experiment, developed over 40 years ago by R. J. Clifton at Brown University enables the study of the dynamic strength of materials at high pressures and strain rates. Traditional PSPI experiments were typically conducted at velocities and corresponding pressures, limiting the experimental conditions not to exceed the Hugoniot Elastic Limit (HEL) of the anvil materials, with typical values of 3–7 GPa. In this work, PSPI experiments are extended to higher pressures, significantly beyond the HEL, approaching 50 GPa, using a powder gun facility at Caltech. The high-pressure and high-velocity impact regimes introduce several experimental challenges which must be overcome: (1) the inelastic behavior of the anvils at high pressures precludes traditional elastic analysis to extract the material’s strength; (2) the potential for slip between impact faces as a result of elevated temperatures and shear forces on the impact surfaces due to higher velocities and pressures; and (3) accurate measurement of the transverse velocity at large normal displacements, resulting from the higher impact velocities. New experimental capabilities have been developed to overcome each of these technical challenges, which include a new all fiber-optic heterodyne transverse velocity interferometer system. New analysis methods that account for the inelastic response of the flyer and anvil plates have also been developed for the accurate extraction of material strength properties from PSPI experiments. Friction and slip were examined, pushing to the limits of their knowledge under these extreme conditions. The new PSPI capabilities have been demonstrated using tungsten carbide and D2 tool steel anvils for measuring the strength of soda–lime glass and magnesium.

Pressure-Induced Topological and Structural Phase Transitions in an Antiferromagnetic Topological Insulator**Supported by the National Key Research and Development Program of China under Grant Nos. 2018YFA0704300 and 2017YFE0131300, the National Natural Science Foundation of China under Grant Nos. U1932217, 11974246, 11874263 and 10225417, and the Natural Science Foundation of Shanghai under Grant No. 19ZR1477300. The authors thank the support from Analytical

Recently, natural van der Waals heterostructures of (MnBi2Te4)m(Bi2Te3)n have been theoretically predicted and experimentally shown to host tunable magnetic properties and topologically nontrivial surface states. We systematically investigate both the structural and electronic responses of MnBi2Te4 and MnBi4Te7 to external pressure. In addition to the suppression of antiferromagnetic order, MnBi2Te4 is found to undergo a metal–semiconductor–metal transition upon compression. The resistivity of MnBi4Te7 changes dramatically under high pressure and a non-monotonic evolution of ρ (T) is observed. The nontrivial topology is proved to persist before the structural phase transition observed in the high-pressure regime. We find that the bulk and surface states respond differently to pressure, which is consistent with the non-monotonic change of the resistivity. Interestingly, a pressure-induced amorphous state is observed in MnBi2Te4, while two high-pressure phase transitions are revealed in MnBi4Te7. Our combined theoretical and experimental research establishes MnBi2Te4 and MnBi4Te7 as highly tunable magnetic topological insulators, in which phase transitions and new ground states emerge upon compression.

Thermo-elastic model for the prediction of thermodynamic properties of high temperature phase change materials under confinement: Isobaric and isochoric regimes

Thermal energy storage through encapsulation of phase change materials is critical for the efficient usage of renewable energy. In this paper, a model is proposed to include thermal and pressure induced density changes in a confined phase change material. To the best of the authors’ knowledge, the local energy balance at the interface and the total mass balance that couple thermal and pressure induced density changes during melting of confined phase change materials are proposed for the first time. The proposed model is solved for a KNO3 salt and several values of the elastic constant in order to probe the phase transition in the whole pressure domain. The behavior of the thermodynamic variables is investigated for other kinds of salts used in high temperature thermal energy storage applications and in the high pressure regime. In all the examples shown, and when the phase change process takes place close to the isochoric regime, the effects of temperature dependent densities are found to be enhanced by pressure induced density changes. However, close to the isobaric regime, the effects of temperature dependent densities are almost negligible. Finally, the thermal energy stored during the melting process is obtained. Close to the isochoric regime, and depending on the types of boundary conditions, the sensible heat stored is found to be enhanced by thermal expansion, while the latent heat absorbed is significantly reduced.

Integrated 3D geomechanical modeling and its application for well planning in Bantumilli South area, Krishna-Godavari Basin, India

Complex geologic structure, a heterogeneous reservoir, and complications related to high pressure during drilling necessitate carrying out geomechanical modeling to understand the physical properties of rocks and fluids present within the Early Cretaceous synrift sequence in the Bantumilli South area of the Krishna-Godavari Basin in India. Reservoirs within the synrift sequence exhibit low permeability and high pore pressure. Identification of safe mud-weight window zones is critical for safe drilling of wells in this part of the basin. A detailed workflow for building a robust 3D geomechanical model and its applications to well planning and hydraulic fracturing are presented. Elastic properties of the reservoirs were estimated by prestack seismic inversion. Elastic properties and pore pressure volumes were used to simulate the 3D stress field. The maximum horizontal stress direction is observed to be 130°N ± 5°, i.e., northwest to southeast, and estimated fracture pressure (minimum horizontal stress) values range between 10,000 and 14,200 psi within the synrift sequence. The study has shown that the Cretaceous section of the reservoir has narrow mud-weight window zones. These zones are governed mainly by a high pore pressure regime in the reservoirs. Additionally, deep-seated basement faults have played an important role in the compartmentalization of the reservoir in terms of geomechanical properties.

In-plane air damping of micro- and nano- mechanical resonators

This study investigates the effect of air damping on in-plane silicon micro/nano-resonators sandwiched between two electrodes (two ports) for sensing and actuation. Experimental measurements are presented for the quality factor (Q) as varying pressure for several case studies of clamped–clamped and clamped–free micro/nano-beam resonators of various geometrical parameters and airgap dimensions. The focus of this work is on large airgap dimensions, where typically squeeze-film damping is assumed negligible. In addition to the fundamental first mode, several results are shown when the resonators are operated near their second or third modes of vibrations. Several curves are generated to show the dependence of the quality factor on the resonator size, boundary condition, and mode order. Several analytical models are applied to investigate the dominant dissipations mechanisms and the models capability to predict Q on both low and higher pressure regimes, and the results are compared to the experimental data.

Closest-Packing Water Monolayer Stably Intercalated in Phyllosilicate Minerals under High Pressure.

The directional hydrogen-bond (HB) network and nondirectional van der Waals (vdW) interactions make up the specificity of water. Directional HBs could construct an ice-like monolayer in hydrophobic confinement even in the ambient regime. Here, we report a water monolayer dominated by vdW interactions confined in a phyllosilicate interlayer under high pressure. Surprisingly, it was in a thermodynamically stable state coupled with bulk water at the same pressure (P) and temperature (T), as revealed by the thermodynamic integration approach on the basis of molecular dynamics (MD) simulations. Both classical and ab initio MD simulations showed water O atoms were stably trapped and exhibited an ordered hexagonal closest-packing arrangement, but OH bonds of water reoriented frequently and exhibited a specific two-stage reorientation relaxation. Strikingly, hydration in the interlayer under high pressure had no relevance with surface hydrophilicity rationalized by the HB forming ability, which, however, determines wetting in the ambient regime. Intercalated water molecules were trapped by vdW interactions, which shaped the closest-packing arrangement and made hydration energetically available. The high pressure-volume term largely drives hydration, as it compensates the entropy penalty which is restricted by a relatively lower temperature. This vdW water monolayer should be ubiquitous in the high pressure but low-temperature regime.

Tunable quantum critical point and detached superconductivity in Al-doped CrAs

The origin of unconventional superconductivity and its relationship to a T = 0 K quantum critical point (QCP), which is hidden inside the dome of a superconducting state, have long been an outstanding puzzle in strongly correlated superconductors. The observation and tuning of the hidden QCP, which is key to resolving the mystery, however, has been rarely reported. Here we report the controlling of a hidden QCP in the helical antiferromagnet CrAs and separation of the tuned QCP from the pressure-induced superconducting phase. The Al doping in CrAs increases the antiferromagnetic ordering temperature TN from 265 to 275 K, while it suppresses the QCP from 8 to 4.5 kbar. Pressure-induced superconductivity in the high-pressure regime is almost independent of Al doping, but superconductivity below 6 kbar is suppressed, revealing the clear separation between the tuned antiferromagnetic QCP and Tc maximum. These discoveries illustrate subtleties in the interplay between superconductivity and quantum criticality and warrant a deeper insight in understanding of unconventional superconductivity.