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1.
J Am Chem Soc ; 2022 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-36399710

RESUMO

2,5-Furandicarboxylic acid (FDCA) is one of the top-12 value-added chemicals from sugar. Besides the wide application in chemical industry, here we found that solid FDCA polymerized to form an atomic-scale ordered sp3-carbon nanothread (CNTh) upon compression. With the help of perfectly aligned π-π stacked molecules and strong intermolecular hydrogen bonds, crystalline poly-FDCA CNTh with uniform syn-configuration was obtained above 11 GPa, with the crystal structure determined by Rietveld refinement of the X-ray diffraction (XRD). The in situ XRD and theoretical simulation results show that the FDCA experienced continuous [4 + 2] Diels-Alder reactions along the stacking direction at the threshold C···C distance of ∼2.8 Å. Benefiting from the abundant carbonyl groups, the poly-FDCA shows a high specific capacity of 375 mAh g-1 as an anode material of a lithium battery with excellent Coulombic efficiency and rate performance. This is the first time a three-dimensional crystalline CNTh is obtained, and we demonstrated it is the hydrogen bonds that lead to the formation of the crystalline material with a unique configuration. It also provides a new method to move biomass compounds toward advanced functional carbon materials.

2.
Proc Natl Acad Sci U S A ; 119(44): e2211243119, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36279458

RESUMO

Water transported by subducted oceanic plates changes mineral and rock properties at high pressures and temperatures, affecting the dynamics and evolution of the Earth's interior. Although geochemical observations imply that water should be stored in the lower mantle, the limited amounts of water incorporation in pyrolitic lower-mantle minerals suggest that water in the lower mantle may be stored in the basaltic fragments of subducted slabs. Here, we performed multianvil experiments to investigate the stability and water solubility of aluminous stishovite and CaCl2-structured silica, referred to as poststishovite, in the SiO2-Al2O3-H2O systems at 24 to 28 GPa and 1,000 to 2,000 °C, representing the pressure-temperature conditions of cold subducting slabs to hot upwelling plumes in the top lower mantle. The results indicate that both alumina and water contents in these silica minerals increase with increasing temperature under hydrous conditions due to the strong Al3+-H+ charge coupling substitution, resulting in the storage of water up to 1.1 wt %. The increase of water solubility in these hydrous aluminous silica phases at high temperatures is opposite of that of other nominally anhydrous minerals and of the stability of the hydrous minerals. This feature prevents the releasing of water from the subducting slabs and enhances the transport water into the deep lower mantle, allowing significant amounts of water storage in the high-temperature lower mantle and circulating water between the upper mantle and the lower mantle through subduction and plume upwelling. The shallower depths of midmantle seismic scatterers than expected from the pure SiO2 stishovite-poststishovite transition pressure support this scenario.

3.
Proc Natl Acad Sci U S A ; 119(41): e2211778119, 2022 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-36191193

Assuntos
Oxigênio
4.
Nat Commun ; 13(1): 4650, 2022 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-35945215

RESUMO

Solids can be generally categorized by their structures into crystalline and amorphous states with different interactions among atoms dictating their properties. Crystalline-amorphous hybrid structures, combining the advantages of both ordered and disordered components, present a promising opportunity to design materials with emergent collective properties. Hybridization of crystalline and amorphous structures at the sublattice level with long-range periodicity has been rarely observed. Here, we report a nested order-disorder framework (NOF) constructed by a crystalline matrix with self-filled amorphous-like innards that is obtained by using pressure to regulate the bonding hierarchy of Cu12Sb4S13. Combined in situ experimental and computational methods demonstrate the formation of disordered Cu sublattice which is embedded in the retained crystalline Cu framework. Such a NOF structure gives a low thermal conductivity (~0.24 W·m-1·K-1) and a metallic electrical conductivity (8 × 10-6 Ω·m), realizing the collaborative improvement of two competing physical properties. These findings demonstrate a category of solid-state materials to link the crystalline and amorphous forms in the sublattice-scale, which will exhibit extraordinary properties.

5.
Nature ; 608(7923): 513-517, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35978124

RESUMO

High pressure induces dramatic changes and novel phenomena in condensed volatiles1,2 that are usually not preserved after recovery from pressure vessels. Here we report a process that pressurizes volatiles into nanopores of type 1 glassy carbon precursors, converts glassy carbon into nanocrystalline diamond by heating and synthesizes free-standing nanostructured diamond capsules (NDCs) capable of permanently preserving volatiles at high pressures, even after release back to ambient conditions for various vacuum-based diagnostic probes including electron microscopy. As a demonstration, we perform a comprehensive study of a high-pressure argon sample preserved in NDCs. Synchrotron X-ray diffraction and high-resolution transmission electron microscopy show nanometre-sized argon crystals at around 22.0 gigapascals embedded in nanocrystalline diamond, energy-dispersive X­ray spectroscopy provides quantitative compositional analysis and electron energy-loss spectroscopy details the chemical bonding nature of high-pressure argon. The preserved pressure of the argon sample inside NDCs can be tuned by controlling NDC synthesis pressure. To test the general applicability of the NDC process, we show that high-pressure neon can also be trapped in NDCs and that type 2 glassy carbon can be used as the precursor container material. Further experiments on other volatiles and carbon allotropes open the possibility of bringing high-pressure explorations on a par with mainstream condensed-matter investigations and applications.

6.
Phys Rev Lett ; 129(1): 016401, 2022 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-35841573

RESUMO

Valence transition could induce structural, insulator-metal, nonmagnetic-magnetic and superconducting transitions in rare-earth metals and compounds, while the underlying physics remains unclear due to the complex interaction of localized 4f electrons as well as their coupling with itinerant electrons. The valence transition in the elemental metal europium (Eu) still has remained as a matter of debate. Using resonant x-ray emission scattering and x-ray diffraction, we pressurize the states of 4f electrons in Eu and study its valence and structure transitions up to 160 GPa. We provide compelling evidence for a valence transition around 80 GPa, which coincides with a structural transition from a monoclinic (C2/c) to an orthorhombic phase (Pnma). We show that the valence transition occurs when the pressure-dependent energy gap between 4f and 5d electrons approaches the Coulomb interaction. Our discovery is critical for understanding the electrodynamics of Eu, including magnetism and high-pressure superconductivity.

7.
J Phys Chem Lett ; 13(18): 4170-4175, 2022 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-35507771

RESUMO

Hydrogen transfer (H-transfer) is an important elementary reaction in chemistry and bioscience. It is often facilitated by the hydrogen bonds between the H-donor and acceptor. Here, at room temperature and high pressure, we found that solid 2-butyne experienced a concerted two-in-two-out intermolecular CH···π H-transfer, which initiated the subsequent polymerization. Such double H-transfer goes through an aromatic Hückel six-membered ring intermediate state via intermolecular CH···π interactions enhanced by external pressure. Our work shows that H-transfer can occur via the CH···π route in appropriate conformations under high pressure, which gives important insights into the H-transfer in solid-state hydrocarbons.


Assuntos
Hidrogênio , Hidrogênio/química , Ligação de Hidrogênio , Conformação Molecular
8.
J Am Chem Soc ; 144(16): 7414-7421, 2022 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-35420809

RESUMO

Identifying ordering in non-crystalline solids has been a focus of natural science since the publication of Zachariasen's random network theory in 1932, but it still remains as a great challenge of the century. Literature shows that the hierarchical structures, from the short-range order of first-shell polyhedra to the long-range order of translational periodicity, may survive after amorphization. Here, in a piece of AlPO4, or berlinite, we combine X-ray diffraction and stochastic free-energy surface simulations to study its phase transition and structural ordering under pressure. From reversible single crystals to amorphous transitions, we now present an unambiguous view of the topological ordering in the amorphous phase, consisting of a swarm of Carpenter low-symmetry phases with the same topological linkage, trapped in a metastable intermediate stage. We propose that the remaining topological ordering is the origin of the switchable "memory glass" effect. Such topological ordering may hide in many amorphous materials through disordered short atomic displacements.

9.
Proc Natl Acad Sci U S A ; 119(17): e2201165119, 2022 04 26.
Artigo em Inglês | MEDLINE | ID: mdl-35439060

RESUMO

Carbon nanothread (CNTh) is a "one-dimensional diamond polymer" that combines high tensile strength and flexibility, but it severely suffers from intrathread disorder. Here, by modifying the reactivity and the stacking ordering of the aromatic precursor, crystalline C3N3H3 CNTh with perfect hexagonal orientation and stacking was synthesized at 10.2 GPa and 573 K from s-triazine. By Rietveld refinement of X-ray diffraction data, gas chromatography mass spectrometry investigation, and theoretical calculation, we found that synthesized CNTh has a tube (3,0) structure, with the repeating s-triazine residue connected solely by C­N bonds along the thread. A "peri-cage" reaction, the concerted bonding between six C and N atoms, instead of [4 + 2] or [1,4] addition reactions, was concluded for the formation of CNThs, and the critical bonding distance between the nearest intermolecular C and N was ∼2.9 Å. The formation of a "structure-specific" crystalline CNTh with C and N orderly distributed highlighted the importance of reaction selectivity and stacking order of reactant molecules, which have great significance for understanding the polymerization of aromatic molecules under high pressure and developing new crystalline CNThs.

10.
Nature ; 602(7896): 258-262, 2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-35140389

RESUMO

Earth's inner core (IC) is less dense than pure iron, indicating the existence of light elements within it1. Silicon, sulfur, carbon, oxygen and hydrogen have been suggested to be the candidates2,3, and the properties of iron-light-element alloys have been studied to constrain the IC composition4-19. Light elements have a substantial influence on the seismic velocities4-13, the melting temperatures14-17 and the thermal conductivities18,19 of iron alloys. However, the state of the light elements in the IC is rarely considered. Here, using ab initio molecular dynamics simulations, we find that hydrogen, oxygen and carbon in hexagonal close-packed iron transform to a superionic state under the IC conditions, showing high diffusion coefficients like a liquid. This suggests that the IC can be in a superionic state rather than a normal solid state. The liquid-like light elements lead to a substantial reduction in the seismic velocities, which approach the seismological observations of the IC20,21. The substantial decrease in shear-wave velocity provides an explanation for the soft IC21. In addition, the light-element convection has a potential influence on the IC seismological structure and magnetic field.

11.
Proc Natl Acad Sci U S A ; 118(51)2021 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-34907019

RESUMO

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 K 0 = 439.2(9) GPa, K 0' = 3.6(1), and shear modulus as G 0 = 533(3) GPa, G 0' = 2.3(3), which are consistent with our first-principles simulation. In contrast to the previous experiment of isothermal equation of state, the K 0' 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.

12.
J Phys Chem Lett ; 12(50): 12055-12061, 2021 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-34905378

RESUMO

Substituted polyacetylene is expected to improve the chemical stability, physical properties, and combine new functions to the polyacetylene backbones, but its diversity is very limited. Here, by applying external pressure on solid acetylenedicarboxylic acid, we report the first crystalline poly-dicarboxylacetylene with every carbon on the trans-polyacetylene backbone bonded to a carboxyl group, which is very hard to synthesize by traditional methods. The polymerization is evidenced to be a topochemical reaction with the help of hydrogen bonds. This unique structure combines the extremely high content of carbonyl groups and high conductivity of a polyacetylene backbone, which exhibits a high specific capacity and excellent cycling/rate performance as a Li-ion battery (LIB) anode. We present a completely functionalized crystalline polyacetylene and provide a high-pressure solution for the synthesis of polymeric LIB materials and other polymeric materials with a high content of active groups.

13.
Materials (Basel) ; 14(24)2021 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-34947173

RESUMO

The discovery of a record high superconducting transition temperature (Tc) of 288 K in a pressurized hydride inspires new hope to realize ambient-condition superconductivity. Here, we give a perspective on the theoretical and experimental studies of hydride superconductivity. Predictions based on the BCS-Eliashberg-Midgal theory with the aid of density functional theory have been playing a leading role in the research and guiding the experimental realizations. To date, about twenty hydrides experiments have been reported to exhibit high-Tc superconductivity and their Tc agree well with the predicted values. However, there are still some controversies existing between the predictions and experiments, such as no significant transition temperature broadening observed in the magnetic field, the experimental electron-phonon coupling beyond the Eliashberg-Midgal limit, and the energy dependence of density of states around the Fermi level. To investigate these controversies and the origin of the highest Tc in hydrides, key experiments are required to determine the structure, bonding, and vibrational properties associated with H atoms in these hydrides.

14.
Proc Natl Acad Sci U S A ; 118(45)2021 11 09.
Artigo em Inglês | MEDLINE | ID: mdl-34725159

RESUMO

Refractory oxygen bound to cations is a key component of the interior of rocky exoplanets. Its abundance controls planetary properties including metallic core fraction, core composition, and mantle and crust mineralogy. Interior oxygen abundance, quantified with the oxygen fugacity (fO2), also determines the speciation of volatile species during planetary outgassing, affecting the composition of the atmosphere. Although melting drives planetary differentiation into core, mantle, crust, and atmosphere, the effect of fO2 on rock melting has not been studied directly to date, with prior efforts focusing on fO2-induced changes in the valence ratio of transition metals (particularly iron) in minerals and magma. Here, melting experiments were performed using a synthetic iron-free basalt at oxygen levels representing reducing (log fO2 = -11.5 and -7) and oxidizing (log fO2 = -0.7) interior conditions observed in our solar system. Results show that the liquidus of iron-free basalt at a pressure of 1 atm is lowered by 105 ± 10 °C over an 11 log fO2 units increase in oxygen abundance. This effect is comparable in size to the well-known enhanced melting of rocks by the addition of H2O or CO2 This implies that refractory oxygen abundance can directly control exoplanetary differentiation dynamics by affecting the conditions under which magmatism occurs, even in the absence of iron or volatiles. Exoplanets with a high refractory oxygen abundance exhibit more extensive and longer duration magmatic activity, leading to more efficient and more massive volcanic outgassing of more oxidized gas species than comparable exoplanets with a lower rock fO2.

15.
J Phys Chem Lett ; 12(44): 10893-10898, 2021 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-34730961

RESUMO

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.

16.
Natl Sci Rev ; 8(4): nwaa096, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34691604

RESUMO

As the reaction product of subducted water and the iron core, FeO2 with more oxygen than hematite (Fe2O3) has been recently recognized as an important component in the D" layer just above the Earth's core-mantle boundary. Here, we report a new oxygen-excess phase (Mg, Fe)2O3+ δ (0 < δ < 1, denoted as 'OE-phase'). It forms at pressures greater than 40 gigapascal when (Mg, Fe)-bearing hydrous materials are heated over 1500 kelvin. The OE-phase is fully recoverable to ambient conditions for ex situ investigation using transmission electron microscopy, which indicates that the OE-phase contains ferric iron (Fe3+) as in Fe2O3 but holds excess oxygen through interactions between oxygen atoms. The new OE-phase provides strong evidence that H2O has extraordinary oxidation power at high pressure. Unlike the formation of pyrite-type FeO2Hx which usually requires saturated water, the OE-phase can be formed with under-saturated water at mid-mantle conditions, and is expected to be more ubiquitous at depths greater than 1000 km in the Earth's mantle. The emergence of oxygen-excess reservoirs out of primordial or subducted (Mg, Fe)-bearing hydrous materials may revise our view on the deep-mantle redox chemistry.

17.
Natl Sci Rev ; 8(4): nwaa098, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34691606

RESUMO

Understanding the mineralogy of the Earth's interior is a prerequisite for unravelling the evolution and dynamics of our planet. Here, we conducted high pressure-temperature experiments mimicking the conditions of the deep lower mantle (DLM, 1800-2890 km in depth) and observed surprising mineralogical transformations in the presence of water. Ferropericlase, (Mg, Fe)O, which is the most abundant oxide mineral in Earth, reacts with H2O to form a previously unknown (Mg, Fe)O2H x (x ≤ 1) phase. The (Mg, Fe)O2H x has a pyrite structure and it coexists with the dominant silicate phases, bridgmanite and post-perovskite. Depending on Mg content and geotherm temperatures, the transformation may occur at 1800 km for (Mg0.6Fe0.4)O or beyond 2300 km for (Mg0.7Fe0.3)O. The (Mg, Fe)O2H x is an oxygen excess phase that stores an excessive amount of oxygen beyond the charge balance of maximum cation valences (Mg2+, Fe3+ and H+). This important phase has a number of far-reaching implications including extreme redox inhomogeneity, deep-oxygen reservoirs in the DLM and an internal source for modulating oxygen in the atmosphere.

18.
Natl Sci Rev ; 8(4): nwab020, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34691625
19.
Natl Sci Rev ; 8(4): nwab018, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34691624

RESUMO

The deep Earth is the engine of whole Earth systems and plays a key role in surface evolution and geological hazards. Scientists have been deciphering the internal processes that shape our habitable planet, especially since the formulation of plate tectonics theory. To date, how the deep Earth works remains mysterious. At the end of 2020, the Chinese Academy of Sciences (CAS) started to set up the Center for Excellence in Deep Earth Science, headquartered in the Guangzhou Institute of Geochemistry (GIG), with long-term support for these emerging and interdisciplinary research areas. NSR recently talked to Professor Yi-Gang Xu, GIG's Director, about why the study of the Earth's interior is essential, the current progress of deep Earth science in China, and what makes our planet habitable.

20.
Natl Sci Rev ; 8(9): nwaa288, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34691729

RESUMO

Metal halide perovskites possess unique atomic and electronic configurations that endow them with high defect tolerance and enable high-performance photovoltaics and optoelectronics. Perovskite light-emitting diodes have achieved an external quantum efficiency of over 20%. Despite tremendous progress, fundamental questions remain, such as how structural distortion affects the optical properties. Addressing their relationships is considerably challenging due to the scarcity of effective diagnostic tools during structural and property tuning as well as the limited tunability achievable by conventional methods. Here, using pressure and chemical methods to regulate the metal off-centering distortion, we demonstrate the giant tunability of photoluminescence (PL) in both the intensity (>20 times) and wavelength (>180 nm/GPa) in the highly distorted halide perovskites [CH3NH3GeI3, HC(NH2)2GeI3, and CsGeI3]. Using advanced in situ high-pressure probes and first-principles calculations, we quantitatively reveal a universal relationship whereby regulating the level of off-centering distortion towards 0.2 leads to the best PL performance in the halide perovskites. By applying this principle, intense PL can still be induced by substituting CH3NH3 + with Cs+ to control the distortion in (CH3NH3)1-xCsxGeI3, where the chemical substitution plays a similar role as external pressure. The compression of a fully substituted sample of CsGeI3 further tunes the distortion to the optimal value at 0.7 GPa, which maximizes the emission with a 10-fold enhancement. This work not only demonstrates a quantitative relationship between structural distortion and PL property of the halide perovskites but also illustrates the use of knowledge gained from high-pressure research to achieve the desired properties by ambient methods.

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