High-pressure Investigations Research Articles

ARTERIAL HYPERTENSION IN A PATIENT OPERATED FOR CONN ADENOMA: ABOUT A CASE

Objective: Conn's adenoma is a rare cause of high blood pressurr. It is the second surgically curable cause of hypertension after renal artery stenosis. Its recurrence after surgery remains rare. Design and method: We report a case. Results: Mr B.M, 60 years old, with a history of diabetes, hypertensive and right adrenalectomy for Conn's adenoma, admitted for investigation of dysphagia and high blood pressure. On examination, the blood pressure was 17/10, the pulses are present and symmetrical. Skin examination revealed sclerodactyly, subcutaneous calcinosis and raynaud's syndrome. The blood ionogram showed hypokalaemia while the renal workup noted chronic renal failure. Urinary cortisol and plasma cortisol were normal. The adrenal CT scan showed a left adrenal nodule. A contralateral recurrence of Conn's adenoma associated with CREST syndrome was strongly suspected. The decision was to intensify the antihypertensive treatment. Conclusions: Hypertension can be multifactorial: metabolic syndrome, Conn's adenoma and systemic disorder. A recurrence of an operated Conn's adenoma should be systematically sought in the presence of persistent elevated blood pressure levels.

A New Superconducting 3R-WS2 Phase at High Pressure.

High-pressure investigation has been shown to be of paramount significance for changing the conventional lattice or bringing fascinating properties, especially inducing superconducting phases. Here we studied the application of pressure to the recently synthesized 2M-WS2 with the record Tc (8.8 K) among transition metal dichalcogenides (TMDs) at ambient pressure by electrical resistance investigations, synchrotron X-ray studies, and theoretical calculations. Tc in the initial 2M-WS2 dropped from the maximum to become undetected, accompanied by a phase transition into a semiconductor, 3R-WS2, at 15 GPa. The successive metallization and superconducting transitions in 3R-WS2 were observed at 48.8 GPa with Tc ≈ 2.5 K. This is the first experimental case in which superconductivity has been realized in the 3R phase among TMDs. We propose that the degradation of superconductivity in 2M-WS2 and the reemergence of superconductivity in 3R-WS2 are mainly attributable to changes in the density of states near the Fermi surface driven by the interlayer coupling.

Stability of the peroxide group inBaO2under high pressure

Alkaline earth metal peroxides are typical examples of ionic compounds containing polyanions. We herein report a stable $\mathrm{Ba}{\mathrm{O}}_{2}$ phase at high pressure up to 130 GPa found via a first-principles computational structure search and high-pressure experimental investigations. The identified monoclinic structure (space group $C2/m$) can be derived by sublattice distortions of Ba atoms and peroxide groups associated with the phonon mode softening of the lower-pressure $Cmmm$ structure. Contrary to the previous expectation of polymerization of the peroxide group at elevated pressure, this phase retains the peroxide group and, interestingly, exhibits an insulating behavior demonstrating an increase of the band gap under compression. Our synchrotron x-ray diffraction (XRD) measurements could not distinguish between $Cmmm$ and $C2/m\mathrm{Ba}{\mathrm{O}}_{2}$ definitively because the difference in XRD patterns is very subtle. However, our data do not show any sign of polymerization transition up to 120 GPa. Raman spectra of the O-O peroxide vibration show a small anomaly in frequency at 110 GPa, which is qualitatively like that predicted theoretically due to the $Cmmm$ to $C2/m$ phase transition, thus supporting the predicted transformation.

Operando high-pressure investigation of size-controlled CuZn catalysts for the methanol synthesis reaction

Although Cu/ZnO-based catalysts have been long used for the hydrogenation of CO2 to methanol, open questions still remain regarding the role and the dynamic nature of the active sites formed at the metal-oxide interface. Here, we apply high-pressure operando spectroscopy methods to well-defined Cu and Cu0.7Zn0.3 nanoparticles supported on ZnO/Al2O3, γ-Al2O3 and SiO2 to correlate their structure, composition and catalytic performance. We obtain similar activity and methanol selectivity for Cu/ZnO/Al2O3 and CuZn/SiO2, but the methanol yield decreases with time on stream for the latter sample. Operando X-ray absorption spectroscopy data reveal the formation of reduced Zn species coexisting with ZnO on CuZn/SiO2. Near-ambient pressure X-ray photoelectron spectroscopy shows Zn surface segregation and the formation of a ZnO-rich shell on CuZn/SiO2. In this work we demonstrate the beneficial effect of Zn, even in diluted form, and highlight the influence of the oxide support and the Cu-Zn interface in the reactivity.

Carbon phase adjustment by multi-configuration ligand in endohedral metallofullerene derivatives Gd@C82(morpholine)7 under high pressure

Abstract Metallofullerenes present an ideal research object for developing new carbon structures with improved properties under high pressure. In this study, high pressure investigation is realized on metallofullerene derivatives (Gd@C82(morpholine)7) by applying in situ synchrotron XRD, Raman, and IR spectroscopy, combined with high pressure density functional theory (DFT) calculations. The regulations of multi-configuration morpholine ligands avoid the direct collapse of the carbon cages commonly happened to fullerenes, making the fine structure transformation possible for the first time, including ligand configuration exchange, anisotropic shrinkage of cage, new constructed bonds, and even the encaged metal’s movement with increasing pressure. The charge-transfer principle as the beneath driving force of structural transition is found. These findings demonstrate that multi-configuration ligand maps an innovative strategy for phase transition control of metallofullerenes under high pressure, thus providing deep insight, step by step, into the phase transition mechanism of these hybrid molecular systems on molecular level.

In situ high temperature and high-pressure investigation of crystal structure and OH of rutile in jadeite quartzite from the Dabie Mountains, China

本文通过金刚石对顶砧与拉曼光谱、红外光谱联用技术，原位模拟了金红石在高温高压下晶体结构及其OH的变化，从而了解俯冲带流体中金红石在地质过程中的行为及作用。实验证明，金红石在压力的作用下经历两次相变，分别为金红石型TiO₂结构→斜锆石型TiO₂结构（P=23.43GPa）→萤石型TiO₂结构（P=34.98GPa），其结构在经历过超深俯冲后、折返过程中则以ɑ-PbO₂型TiO₂结构稳定存在。并且金红石晶体中的OH红外特征峰强度随着压力的增加而降低，从而显示在加压过程中金红石中OH含量降低，但直至地球深部超过600km（37.28GPa，约1200km），其晶体中的OH也并未完全脱去。在高温高压实验中，金红石样品从常温常压条件加压、加温至P=4.01~4.08GPa和T=700℃时，金红石晶体的有序度、OH含量随着温度增加而降低，但至实验最高温压，晶体内部仍保留OH，其结构也稳定存在，因此金红石可以将水携带至深部约120km处。在降至常温常压的过程中，金红石中OH含量虽然增加，但并未恢复至实验开始时的含量，因此经历过快速俯冲、折返后的金红石中的OH含量无法代表金红石形成时的OH含量。;In this paper, the crystal structure and OH changes of rutile under high temperature and pressure were simulated in situ by means of diamond anvil cell combined with Raman spectroscopy and infrared spectroscopy, so as to understand the behavior and role of rutile in the subduction zone fluid during the geological process. The experimental results show that rutile underwent two phase transitions under the action of pressure, respectively: rutile type TiO₂→baddeleyite phase of TiO₂ structure (P=23.43GPa)→fluorite of TiO₂ structure (P=34.98GPa). The structure of TiO₂ is stable as ɑ-PbO₂ of TiO₂ structure after the ultra-deep subduction and exhumation. And with the increase of pressure, the intensity of infrared characteristic peak of rutile will decrease, which leads to the decompression of OH content of rutile in the decrease of pressure process. But until it subducted to a depth of more than 600km (37.28GPa), the OH of rutile is not completely removed. In the high temperature and high-pressure experiments, the rutile sample is stable when it is pressurized from room temperature and pressure to P=4.01~4.08GPa and T=700℃. With the increase of temperature, the stability of rutile crystal increases and the content of OH decreases. However, the OH in rutile crystal does not completely remove at the highest temperature and pressure, therefore rutile can carry water to the depth of about 120km. Although the OH content of rutile increased during the process of falling to room temperature, it did not return to the content at the beginning of the experiment. Therefore, the OH content of the rutile after rapid subduction and exhumation cannot represent the initial OH content of the rutile formation.

Effect of radiation on compressibility of hot dense sodium and iron plasma using improved screened hydrogenic model with l splitting

High pressure investigations of matter involve the study of strong shock wave dynamics within the materials which gives rise to many thermal effects leading to dissociation of molecules, ionization of atoms, and radiation emission, etc. The response of materials experiencing a strong shock can be determined by its shock Hugoniot calculations which are frequently applied in numerical and experimental studies in inertial confinement fusion, laboratory astrophysical plasma, etc. These studies involve high energy density plasmas in which the radiation plays an important role in determining the energy deposition and maximum compressibility achieved by the shock within material. In this study, we present an investigation for the effect of radiation pressure on the maximum compressibility of the material using shock Hugoniot calculations. In shock Hugoniot calculations, an equation of state (EOS) is developed in which electronic contributions for EOS calculations are taken from an improved screened hydrogenic model with –l splitting (I-SHML) [High Energy Density Physics (2018) 26 48] under local thermodynamic equilibrium (LTE) conditions. The thermal ionic part calculations are adopted from the state of the art Cowan model while the cold ionic contributions are adopted from the scaled binding energy model. The Shock Hugoniot calculations are carried out for sodium and iron plasmas and our calculated results show excellent agreement with published results obtained by using either sophisticated self-consistent models or the first principle study.

Structural and electrical transport properties of PbS quantum dots under high pressure

The high-pressure investigation of the PbS nanocrystal quantum dots (NQDs) with large Bohr radius has been conducted by in situ high-pressure X-ray diffraction, high-resolution transmission electron microscopy and alternating current impedance spectroscopy experiments up to 41.0 GPa. PbS NQDs present a similar pressure-induced structure phase transition path to bulk and nanocrystal PbS. The electronic conduction and the ionic conduction coexist in PbS NQDs, and the resistivity is generally larger than bulk and nanocrystal PbS. Above 9.1 GPa, the deviatoric stress drives the fusion of the nanoparticles, which leads to the reduction or the disappearance of grain boundary effect as well as a great influence on the dielectric performance.

High pressure Raman spectroscopic study of phase transformations in Zn(CN)2

High-pressure Raman investigations in Zn(CN)2 has been reported up to a pressure of 10 GPa under hydrostatic and non-hydrostatic conditions. We observe several changes in the spectra including splitting of existing modes, broadening of Raman modes and sudden changes in the slope of the frequency vs pressure curve at ≈1 and 1.6 GPa which indicate that the crystal undergoes phase transitions at these pressures. The crystal amorphizes at the highest pressure of 10 GPa. On gradual pressure reduction and total pressure release, the sample doesnot return to its original phase. This indicates that Zn(CN)2 transforms irreversibly to an amorphous phase.

High-temperature and high-pressure NMR investigations of low viscous fluids confined in mesoporous systems

Abstract In this contribution, the relaxation and diffusional behaviors of low viscous fluids, water and methanol confined into mesoporous silica and controlled size pore glass were investigated. The engineered porous systems are relevant to geologically important subsurface energy materials. The engineered porous proxies were characterized by Brunauer–Emmett–Teller (BET) surface analyzer, nuclear magnetic resonance (NMR) spectroscopy, and electron microscopy (EM) to determine surface area, pore-wall protonation and morphology of these materials, respectively. The confined behavior of the low viscous fluids was studied by varying pore diameter, fluid-to-solid ratio, temperature, and pressure, and then compared to bulk liquid state. Both relaxation and diffusion behaviors for the confined fluids showed increasing deviation from pure bulk fluids as the fluid-to-solid ratio was decreased, and surface-to-volume ratio (S/V) was varied. Variable pressure deuteron NMR relaxation of confined D2O and confined methanol, deuterated at the hydroxyl or methyl positions, were performed to exploit the sensitivity of the deuteron quadrupole moment to molecular rotation. The methanol results demonstrated greater pressure dependence than those for water only in bulk. The deviations from bulk liquid behavior arise from different reasons such as confinement and the interactions between confined fluid and the nano-pore wall. The results of the present report give insight into the behavior of low viscosity fluid in nano-confined geometries under different state conditions.

Wurtzite quantum well structures under high pressure

Quantum well systems based on semiconductors with the wurtzite crystalline structure have found widespread applications in photonics and optoelectronic devices, such as light-emitting diodes, laser diodes, or single-photon emitters. In these structures, the radiative recombination processes can be affected by (i) the presence of strain and polarization-induced electric fields, (ii) quantum well thickness fluctuations and blurring of a well–barrier interface, and (iii) the presence of dislocations and native point defects (intentional and unintentional impurities). A separate investigation of these phenomena is not straightforward since they give rise to similar effects, such as a decrease of luminescence efficiency and decay rate, enhancement of the Stokes shift, and strong blueshift of the emission with increasing pump intensity. In this Perspective article, we review the usefulness of measurements of the quantum well luminescence as a function of the hydrostatic pressure for both scientific research and the development of light-emitting technologies. The results presented here show that high-pressure investigations combined with ab initio calculations can identify the nature of optical transitions and the main physical factors affecting the radiative efficiency in quantum well systems. Finally, we will discuss an outlook to the further possibilities to gain new knowledge about the nature of recombination processes in quantum wells using high-pressure spectroscopy.

Properties of Charge Carrier Traps in Lu2O3:Tb,Hf Ceramic Storage Phosphors Observed by High-Pressure Spectroscopy and Photoconductivity

In this work, the kinetic study of charge carrier trapping processes, photocurrent excitation measurements, and high-pressure spectroscopy investigation of an optically stimulated luminescence (OSL) process in Lu2O3:Tb,Hf ceramics are presented. The OSL process was experimentally and theoretically treated to explain the OSL mechanism and kinetics. The obtained results allowed to propose an energetic structure of the system and a theoretical model that explains the charge exchange between Hf4+ and Tb3+ (upon charging the system). It was shown that the OSL took place via the conduction band and the depths of Hf traps were determined for the thermal (1.36 eV) and optical (2.95 eV) release and the significant difference between these two values was fully justified.

Highly tunable properties in pressure-treated two-dimensional Dion–Jacobson perovskites

The application of pressure can achieve novel structures and exotic phenomena in condensed matters. However, such pressure-induced transformations are generally reversible and useless for engineering materials for ambient-environment applications. Here, we report comprehensive high-pressure investigations on a series of Dion-Jacobson (D-J) perovskites A'A n-1Pb n I3n+1 [A' = 3-(aminomethyl) piperidinium (3AMP), A = methylammonium (MA), n = 1, 2, 4]. Our study demonstrates their irreversible behavior, which suggests pressure/strain engineering could viably improve light-absorber material not only in situ but also ex situ, thus potentially fostering the development of optoelectronic and electroluminescent materials. We discovered that the photoluminescence (PL) intensities are remarkably enhanced by one order of magnitude at mild pressures. Also, higher pressure significantly changes the lattices, boundary conditions of electronic wave functions, and possibly leads to semiconductor-metal transitions. For (3AMP)(MA)3Pb4I13, permanent recrystallization from 2D to three-dimensional (3D) structure occurs upon decompression, with dramatic changes in optical properties.

High-pressure investigations on the isostructural phase transition and metallization in realgar with diamond anvil cells

The high-pressure structural, vibrational and electrical properties for realgar were investigated by in-situ Raman scattering and electrical conductivity experiments combined with first-principle calculations up to ~30.8 ​GPa. It was verified that realgar underwent an isostructural phase transition at ~6.3 ​GPa and a metallization at a higher pressure of ~23.5 ​GPa. The isostructural phase transition was well evidenced by the obvious variations of Raman peaks, electrical conductivity, crystal parameters and the As–S bond length. The phase transition of metallization was in closely associated with the closure of bandgap rather than caused by the structural phase transition. And furthermore, the metallic realgar exhibited a relatively low compressibility with the unit cell volume V0 ​= ​718.1.4 ​Å3 and bulk modulus B0 ​= ​36.1 ​GPa.

High pressure investigation of an organic three-dimensional Dirac semimetal candidate having a diamond lattice

$(\mathrm{ET}){\mathrm{Ag}}_{4}{(\mathrm{CN})}_{5}$ [ET = BEDT-TTF: bis(ethylenedithio)tetrathiafulvalene] is a rare example of organic conductors that crystallizes in a diamond structure due to the tetrahedral arrangement of neighboring ET molecules. Because each ET has a $+1$ site charge, the band is half filled, which in combination with strong Coulomb interactions, turn $(\mathrm{ET}){\mathrm{Ag}}_{4}{(\mathrm{CN})}_{5}$ into a Mott insulator. Recently, it was realized that this material may realize a nodal Dirac semimetal with a diamondlike lattice, whose state can be induced by suppressing the strong electron correlations. In this report, we present high pressure transport and optical studies on $(\mathrm{ET}){\mathrm{Ag}}_{4}{(\mathrm{CN})}_{5}$. Our transport study indicates that the activation energy is highly suppressed by the application of hydrostatic pressure. At high pressures, the system varies from activated behavior into Coulomb gap variable range hopping.

Velocity and Stability of Condensed Polymorphic SiH4: A High-Temperature High-Pressure Brillouin Investigation**Supported by the National Key Research and Development Program (Grant No. 2017YFA0403704), the National Natural Science Foundation of China (Grant Nos. 11474127, 11574112, 11274137, and 11504127), the Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT1132), and China Postdoctoral Science Foundation (Grant No. 2015M570265).

Silane (SiH4) is a promising hydrogen-rich compound for pursing high temperature superconducting. Previous high pressure measurements of Raman, x-ray diffraction and theoretical studies on SiH4 mainly focused on its polymorphic structures above 50 GPa, while the structure and the stability under lower pressure range are still unclear. Here we report an investigation of condensed SiH4 by Brillouin scattering measurements at high temperature up to 407 K and high pressure up to 18 GPa. Brillouin scattering frequencies of fluid SiH4 under compression are obtained under isothermal conditions of 300 K, 359 K and 407 K. The SiH4 becomes unstable with increasing temperature and subsequently decomposes into silicon and H2. We find that compression at room temperature induces two velocity anomalies corresponding to a fluid-solid state transition and a phase IV to phase V transition, respectively. Brillouin scattering spectra has been a powerful tool to investigate the fruitful phases and structure transitions in the hydrogen-rich compound under extreme conditions.

Pressure Effects on the Electronic and Optical Properties in Low-Dimensional Metal Halide Perovskites.

Metal halide perovskites have shown enormous potential in perovskite solar cells and light-emitting diodes and made unprecedented progress in the past decade. Pressure engineering as an effective technique can systematically modify the electronic structures and physical properties of functional materials. Low-dimensional metal halide perovskites (0D, 1D, and 2D) with a variety of compositions have soft lattices that allow pressure to drastically modulate their structures and properties. High-pressure investigations have obtained a comprehensive understanding of their structure-property relationships. Simultaneously, discoveries of novel pressure-driven properties, such as metallization and partially retained band gap narrowing have contributed significantly to the further development of such materials. In this Perspective, we mainly highlight the effect of pressure on the properties and structures of low-dimensional metal halide perovskites, which is essential for designing new perovskite materials and advancing applications.

Pressure-induced instability of the fergusonite phase of EuNbO4 studied by in situ Raman spectroscopy, x-ray diffraction, and photoluminescence spectroscopy

In this article, we present high-pressure experimental investigations on EuNbO4, an interesting technologically important material, using synchrotron based x-ray powder diffraction, Raman spectroscopy, and europium photoluminescence measurements up to 39.2, 31.6, and 32.4 GPa, respectively. All three techniques show the stability of the ambient monoclinic phase until 20 GPa. Beyond that, a pressure-induced structural phase transition takes place with the coexistence of two phases over a wide pressure range. The structure of the high-pressure phase has been determined as orthorhombic (space group: Imma) with a volume discontinuity of nearly 9% at the transition indicating the nature of transition to be first order. The high-pressure phase remains stable up to ∼40 GPa. The equation of state data for both phases have been determined, and the modulus of incompressibility indicates that the high-pressure phase with bulk modulus as 246(29) GPa is less compressible compared to the low-pressure phase having bulk modulus as 138(4) GPa. The transition involves a change in the coordination polyhedron around europium, increasing the coordination number from 8 in the fergusonite to 12 in the orthorhombic phase, while the coordination around niobium remains 4 in both the phases. All the 18 expected Raman modes in the fergusonite structure have been observed, and their variation as a function of pressure has been reported. The mode Grüneisen parameters for the observed Raman frequencies for monoclinic and orthorhombic phases have been determined. Europium photoluminescence spectra show drastic changes near the transition pressure, which point toward changes in the local environment around the europium ion.

High-Pressure Behavior of Nickel Sulfate Monohydrate: Isothermal Compressibility, Structural Polymorphism, and Transition Pathway.

Single crystals of synthetic nickel sulfate monohydrate, α-NiSO4·H2O (space-group symmetry C2/c at ambient conditions), were subject to high-pressure behavior investigations in a diamond-anvil cell up to 10.8 GPa. By means of subtle spectral changes in Raman spectra recorded at 298 K on isothermal compression, two discontinuities were identified at 2.47(1) and 6.5(5) GPa. Both transitions turn out to be apparently second order in character, as deduced from the continuous evolution of unit-cell volumes determined from single-crystal X-ray diffraction. The first structural transition from α- to β-NiSO4·H2O is an obvious ferroelastic C2/c–P1̅ transition. It is purely displacive from a structural point of view, accompanied by symmetry changes in the hydrogen-bonding scheme. The second β- to γ-NiSO4·H2O transition, further splitting the O2 (hydrogen bridge acceptor) position and violating the P1̅ space-group symmetry, is also evident from the splitting of individual bands in the Raman spectra. It can be attributed to symmetry reduction through local violation of local centrosymmetry. Lattice elasticities were obtained by fitting second-order Birch–Murnaghan equations of state to the p-V data points yielding the following zero-pressure bulk moduli values: K0 = 63.4 ± 1.0 GPa for α-NiSO4·H2O, K0 = 61.3 ± 1.9 GPa for β-NiSO4·H2O, and K0 = 68.8 ± 2.5 GPa for γ-NiSO4·H2O.

High-silica mordenite as scaffold for phenylacetylene polymerization: In situ high pressure investigation

Abstract The joint use of high pressure and regular void-space architectures is a promising route to obtain new nanomaterials with unique properties. We explore herein the pressure-driven injection of aromatic guest species inside zeolite mordenite. Monomeric phenylacetylene (PhA), used as pressure transmitting medium, was inserted in high-silica mordenite at high pressure conditions. In-situ X-ray powder diffraction and IR spectroscopy analyses show that the combined action of high pressure, temperature and zeolite pores accomplish the intrusion of phenylacetylene and its conversion to oligomeric species exhibiting a greater degree of conjugation with respect to the starting monomer. This study may open a new path for the realization of composite materials with interesting optoelectronic properties via pressure-driven intrusion and polymerization of aromatic molecules inside zeolite frameworks.