High-Pressure Polymerization of Phenol toward Degree-4 Carbon Nanothread.

Saturated sp-carbon nanothreads (CNTh) have garnered significant interest due to their predicted high Young's modulus and thermal conductivity. While the incorporation of heteroatoms into the central ring has been shown to influence the formation of CNTh and yield chemically homogeneous products, the impact of pendant groups on the polymerization process remains underexplored. In this study, we investigate the pressure-induced polymerization of phenol, revealing two phase transitions occurring below 0.

Sulfur chains glass formed by fast compression.

Due to the sulfur's atoms' propensity to form molecules and/or polymeric chains of various sizes and configuration, elemental sulfur possesses more allotropes and polymorphs than any other element at ambient conditions. This variability of the starting building blocks is partially responsible for its rich and fascinating phase diagram, with pressure and temperature changing the states of sulfur from insulating molecular rings and chains to semiconducting low- and high-density amorphous configurations to incommensurate superconducting metallic atomic phase. Here, using a fast compression technique, we demonstrate that the rapid pressurisation of liquid sulfur can effectively break the molecular ring structure, forming a glassy polymeric state of pure-chain molecules (Am-S).

Pressure aging: An effective process to liberate the power of high-pressure materials research.

High pressure can create extreme conditions that enable the formation of novel materials and the discovery of new phenomena. However, the ability to preserve the desirable characteristics of materials obtained under high pressure has remained an elusive challenge, as the pressure-induced changes are typically reversible, except for the pressure-induced chemical reactions such as polymerization of hydrocarbons. Here, we propose the concept of "pressure aging" (PA) that enables the permanent locking-in of high-pressure structures and their associated enhanced properties in functional materials.

The Transformation Mechanism of Graphite to Hexagonal Diamond under Shock Conditions.

The formation of a hexagonal diamond represents one of the most intriguing questions in materials science. Under shock conditions, the graphite basal plane tends to slide and pucker to form diamond. However, how the shock strength determines the phase selectivity remains unclear.

Pressure-induced hydrogen-dominant high-temperature superconductors.

The century-old pursuit of room temperature superconductivity has finally been reached in highly compressed hydrogen-dominant compounds. Future efforts will be focused on understanding the high-pressure hydrogen physics and ambient-pressure applications.

Magnetic methods in studies of new superconducting hydrides in a diamond anvil cell.

This short perspective article summarizes the growing experimental evidence supporting the original claims about hydrogen-rich "superhydrydes" as members of a new family of nearly room temperature BCS superconductors, with hydrogen sub-lattice pre-compressed to the metallic and superconducting state, exactly as predicted in earlier and more recent theoretical works.

Pressure stabilizes ferrous iron in bridgmanite under hydrous deep lower mantle conditions.

Earth's lower mantle is a potential water reservoir. The physical and chemical properties of the region are in part controlled by the Fe/ΣFe ratio and total iron content in bridgmanite. However, the water effect on the chemistry of bridgmanite remains unclear.

Iron silicate perovskite and postperovskite in the deep lower mantle.

Ferromagnesian silicates are the dominant constituents of the Earth's mantle, which comprise more than 80% of our planet by volume. To interpret the low shear-velocity anomalies in the lower mantle, we need to construct a reliable transformation diagram of ferromagnesian silicates over a wide pressure-temperature () range. While MgSiO in the perovskite structure has been extensively studied due to its dominance on Earth, phase transformations of iron silicates under the lower mantle conditions remain unresolved.

Electride Formation of HCP-Iron at High Pressure: Unraveling the Origin of the Superionic State of Iron-Rich Compounds in Rocky Planets.

Electride possesses electrons localized at interstitial sites without attracting nuclei. It brings outstanding material properties not only originating from its own loosely bounded characteristics but also serving as a quasiatom, which even chemically interacts with other elemental ions. In elemental metals, electride transitions have been reported in alkali metals where valence electrons can easily gain enough kinetic energy to escape nuclei.

Structure Responsible for the Superconducting State in LaNiO at High-Pressure and Low-Temperature Conditions.

Very recently, a new superconductor with = 80 K has been reported in nickelate (LaNiO) at around 15-40 GPa conditions (Nature, 621, 493, 2023), which is the second type of unconventional superconductor, besides cuprates, with above liquid nitrogen temperature. However, the phase diagram plotted in this report was mostly based on the transport measurement under low-temperature and high-pressure conditions, and the assumed corresponding X-ray diffraction (XRD) results were carried out at room temperature. This encouraged us to carry out in situ high-pressure and low-temperature synchrotron XRD experiments to determine which phase is responsible for the high state.

Silica-water superstructure and one-dimensional superionic conduit in Earth's mantle.

Water in Earth's deep interior is predicted to be hydroxyl (OH) stored in nominally anhydrous minerals, profoundly modulating both structure and dynamics of Earth's mantle. Here, we use a high-dimensional neuro-network potential and machine learning algorithm to investigate the weight percent water incorporation in stishovite, a main constituent of the subducted oceanic crust. We found that stishovite and water prefer forming medium- to long-range ordered superstructures, featuring one-dimensional (1D) water channels.

The stability of FeH and hydrogen transport at Earth's core mantle boundary.

Iron hydride in Earth's interior can be formed by the reaction between hydrous minerals (water) and iron. Studying iron hydride improves our understanding of hydrogen transportation in Earth's interior. Our high-pressure experiments found that face-centered cubic (fcc) FeH (x ≤ 1) is stable up to 165 GPa, and our ab initio molecular dynamics simulations predicted that fcc FeH transforms to a superionic state under lower mantle conditions.

Pressure-induced nonmonotonic cross-over of steady relaxation dynamics in a metallic glass.

Relaxation dynamics, as a key to understand glass formation and glassy properties, remains an elusive and challenging issue in condensed matter physics. In this work, in situ high-pressure synchrotron high-energy X-ray photon correlation spectroscopy has been developed to probe the atomic-scale relaxation dynamics of a cerium-based metallic glass during compression. Although the sample density continuously increases, the collective atomic motion initially slows down as generally expected and then counterintuitively accelerates with further compression (density increase), showing an unusual nonmonotonic pressure-induced steady relaxation dynamics cross-over at ~3 GPa.

Quantifying the partial ionization effect of gold in the transition region between condensed matter and warm dense matter.

It is now well known that solids under ultra-high-pressure shock compression will enter the warm dense matter (WDM) regime which connects condensed matter and hot plasma. How condensed matter turns into the WDM, however, remains largely unexplored due to the lack of data in the transition pressure range. In this letter, by employing the unique high-Z three-stage gas gun launcher technique developed recently, we compress gold into TPa shock pressure to fill the gap inaccessible by the two-stage gas gun and laser shock experiments.

Oxygen-Driven Enhancement of the Electron Correlation in Hexagonal Iron at Earth's Inner Core Conditions.

Earth's inner core (IC) consists of mainly iron with some light elements. Understanding its structure and related physical properties has been elusive as a result of its required extremely high pressure and temperature conditions. The phase of iron, elastic anisotropy, and density-velocity deficit at the IC have long been questions of great interest.

Superionic effect and anisotropic texture in Earth's inner core driven by geomagnetic field.

Seismological observations suggest that Earth's inner core (IC) is heterogeneous and anisotropic. Increasing seismological observations make the understanding of the mineralogy and mechanism for the complex IC texture extremely challenging, and the driving force for the anisotropic texture remains unclear. Under IC conditions, hydrogen becomes highly diffusive like liquid in the hexagonal-close-packed (hcp) solid Fe lattice, which is known as the superionic state.

Piezovoltaics from PdH.

Metal hydrides have wide applications in energy science. A large pressure gradient propels the hydrogen atoms out. A piezovoltaic device, a pressure gradient-driven battery, can therefore be realized when the migrations of protons and electrons are separated by different conductors.

Ordered Van der Waals Hetero-nanoribbon from Pressure-Induced Topochemical Polymerization of Azobenzene.

Pressure-induced topochemical polymerization of molecular crystals with various stackings is a promising way to synthesize materials with different co-existing sub-structures. Here, by compressing the azobenzene crystal containing two kinds of intermolecular stacking, we synthesized an ordered van der Waals carbon nanoribbon (CNR) heterostructure in one step. Azobenzene polymerizes via a [4 + 2] hetero-Diels-Alder (HDA) reaction of phenylazo-phenyl in layer A and a -polymerization reaction of phenyl in layer B at 18 GPa, as evidenced by in situ Raman and IR spectroscopies, X-ray diffraction, as well as gas chromatography-mass spectrometry and the solid-state nuclear magnetic resonance of the recovered products.

Stabilization of SO at high pressure: implications for the sulfur-excess paradox.

The amount of sulfur in SO discharged in volcanic eruptions exceeds that available for degassing from the erupted magma. This geological conundrum, known as the "sulfur excess", has been the subject of considerable interests but remains an open question. Here, in a systematic computational investigation of sulfur-oxygen compounds under pressure, a hitherto unknown SO compound containing a mixture of sulfur oxidation states +II and +IV is predicted to be stable at pressures above 79 GPa.

From Biomass to Functional Crystalline Diamond Nanothread: Pressure-Induced Polymerization of 2,5-Furandicarboxylic Acid.

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 sp-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 -configuration was obtained above 11 GPa, with the crystal structure determined by Rietveld refinement of the X-ray diffraction (XRD).

Superhydrous aluminous silica phases as major water hosts in high-temperature lower mantle.

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 CaCl-structured silica, referred to as poststishovite, in the SiO-AlO-HO 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.