A5003181622- High-pressure geophysics and materials
- Physics of Superconductivity and Magnetism
- Rare-earth and actinide compounds
- Diamond and Carbon-based Materials Research
- Advanced Condensed Matter Physics
- Advanced Chemical Physics Studies
- Iron-based superconductors research
- Geological and Geochemical Analysis
- X-ray Diffraction in Crystallography
- Magnetic and transport properties of perovskites and related materials
- Superconductivity in MgB2 and Alloys
- Crystal Structures and Properties
- Quantum, superfluid, helium dynamics
- Crystallization and Solubility Studies
- Hydrogen Storage and Materials
- Boron and Carbon Nanomaterials Research
- Inorganic Fluorides and Related Compounds
- Force Microscopy Techniques and Applications
- Crystallography and Radiation Phenomena
- Iron oxide chemistry and applications
- Magnetic Properties of Alloys
- Multiferroics and related materials
- Electronic and Structural Properties of Oxides
- Chemical Thermodynamics and Molecular Structure
- Organic and Molecular Conductors Research
Shanghai Advanced Research Institute
2024-2025
Center for High Pressure Science and Technology Advanced Research
2019-2024
Center for High Pressure Science & Technology Advanced Research
2024
Carnegie Institution for Science
2013-2022
Geophysical Laboratory
2013-2022
Center for High Pressure Science & Technology Advanced Research
2021
Russian Academy of Sciences
1989-2020
University of Chicago
2004-2020
Institute for Nuclear Research
2020
Federal Scientific Research Centre Crystallography and Photonics
2020
Recent predictions and experimental observations of high T_{c} superconductivity in hydrogen-rich materials at very pressures are driving the search for vicinity room temperature. We have developed a novel preparation technique that is optimally suited megabar pressure syntheses superhydrides using modulated laser heating while maintaining integrity sample-probe contacts electrical transport measurements to 200 GPa. detail synthesis characterization lanthanum superhydride samples, including...
High-pressure Raman, infrared, x-ray, and neutron studies show that H2 H2O mixtures crystallize into the sII clathrate structure with an approximate H2/H2O molar ratio of 1:2. The cages are multiply occupied, a cluster two molecules in small cage four large cage. Substantial softening splitting hydrogen vibrons indicate increased intermolecular interactions. quenched is stable up to 145 kelvin at ambient pressure. Retention such high temperatures could help its condensation planetary nebulae...
We measured the spin state of iron in ferropericlase (Mg0.83Fe0.17)O at high pressure and found a high-spin to low-spin transition occurring 60- 70-gigapascal range, corresponding depths 2000 kilometers Earth's lower mantle. This implies that partition coefficient between magnesium silicate perovskite, two main constituents mantle, may increase by several orders magnitude, depleting perovskite phase its iron. The mantle then be composed different layers. upper layer would consist mixture...
The negatively charged nitrogen-vacancy (NV-) center in diamond has realized new frontiers quantum technology. Here, the center's optical and spin resonances are observed under hydrostatic pressures up to 60 GPa. Our observations motivate powerful techniques measure pressure image high magnetic electric phenomena. further reveal a fundamental inadequacy of current model provide insight into its electronic structure.
Pressure-stabilized hydrides are a new rapidly growing class of high-temperature superconductors which is believed to be described within the conventional phonon-mediated mechanism coupling. Here we report synthesis yttrium hexahydride Im3m-YH$_6$ that demonstrates superconducting transition with T$_c$ = 224 K at 166 GPa, much lower than theoretically predicted (>270 K). The measured upper critical magnetic field B$_c$$_2$(0) YH$_6$ was found 116-158 T, 2-2.5 times larger calculated value. A...
Protonated and deuterated ices (H2O D2O) compressed to a maximum pressure of 210 gigapascals at 85 300 kelvin exhibit phase transition 60 in H2O ice (70 D2O ice) on the basis their infrared reflectance spectra determined with synchrotron radiation. The is characterized by soft-mode behavior nu3 O-H or O-D stretch below transition, followed hardening (positive shift) above it. This interpreted as transformation VII structure symmetric hydrogen bonds. spectroscopic features persisted pressures...
Metals formed from light elements are predicted to exhibit intriguing states of electronic order. Of these materials, those containing boron considerable current interest because their relatively high superconducting temperatures. We have investigated elemental very pressure using diamond anvil cell electrical conductivity techniques. find that transforms a nonmetal superconductor at about 160 gigapascals (GPa). The critical temperature the transition increases 6 kelvin (K) 175 GPa 11.2 K...
We report phonon densities of states (DOS) iron measured by nuclear resonant inelastic x-ray scattering to 153 gigapascals and calculated from ab initio theory. Qualitatively, they are in agreement, but the theory predicts density at higher energies. From DOS, we derive elastic thermodynamic parameters iron, including shear modulus, compressional velocities, heat capacity, entropy, kinetic energy, zero-point Debye temperature. In comparison velocities preliminary reference Earth model (PREM)...
Detailed study of the equation state, elasticity, and hardness selected superconducting transition-metal nitrides reveals interesting correlations among their physical properties. Both bulk modulus Vickers are found to decrease with increasing zero-pressure volume in NbN, HfN, ZrN. The computed elastic constants from first principles satisfy c11 > c12 c44 for but HfN ZrN, which good agreement neutron scattering data. cubic delta-NbN phase possesses a 348 GPa, comparable that boron nitride,...
High-pressure Raman measurements of ${\mathrm{H}}_{2}\mathrm{O}$ ice using synthetic diamond anvils reveal major changes associated with the transition to nonmolecular, symmetric hydrogen-bonded state. At 60 GPa strongly pressure-dependent O-H stretching mode disappears, and translational modes exhibit frequency damping anomalies. With further increase in pressure, a single peak appears becomes dominant feature spectrum megabar range. The band is assigned predicted Raman-active O-O...
Superconductivity in compressed lithium is observed by magnetic susceptibility and electrical resistivity measurements. A superconducting critical temperature (Tc) found ranging from 9 to 16 kelvin at 23 80 gigapascals. The pressure dependence of Tc suggests multiple phase transitions, consistent with theoretical predictions reported x-ray diffraction results. values for are much lower than those theoretically predicted, indicating that more sophisticated treatments similar proposed metallic...
Mineral properties in Earth's lower mantle are affected by iron electronic states, but representative pressures and temperatures have not yet been probed. Spin states of lower-mantle ferropericlase measured up to 95 gigapascals 2000 kelvin with x-ray emission a laser-heated diamond cell. A gradual spin transition occurs over pressure-temperature range extending from about 1000 kilometers depth 1900 2200 2300 the mantle. Because low-spin exhibits higher density faster sound velocities...
The elastic properties of selected transition-metal (TM) nitrides and carbides in ${B}_{1}$ structure are studied using the ab initio density-functional perturbation theory. We find that (1) inequality $B>{G}^{\ensuremath{'}}>G>0$ holds for all these materials, where $B=({C}_{11}+2{C}_{12})∕3$, ${G}^{\ensuremath{'}}=({C}_{11}\ensuremath{-}{C}_{12})∕2$, $G={C}_{44}$ with ${C}_{ij}$ constants, (2) $G$ has large values when number electrons per unit cell ${Z}_{V}=8$ or 9. fitted curve vs....
The electronic spin state of iron in lower mantle perovskite is one the fundamental parameters that governs physics and chemistry most voluminous massive shell Earth. We present experimental evidence for spin-pairing transition aluminum-bearing silicate (Mg,Fe)(Si,Al)O(3) under pressures. Our results demonstrate as pressure increases, transforms gradually from initial high-spin toward final low-spin state. At 100 GPa, both aluminum-free samples exhibit a mixed residual magnetic moment...
The two widely accepted mechanisms of the insulator-metal Mott--Hubbard transitions which have been considered up until now are driven by band-filling or bandwidth effects. We found a different mechanism transition, is controlled instead changes in energy $U$. In contrast to $W$ ``bandwidth control'' scenario variations $n$ parameter ``band-filling'' scenario, dramatic decrease $U$ plays key role this mechanism. experimentally observed type insulator metal transition oxide...
Optical absorption spectra have been measured at pressures up to 80 gigapascals (GPa) for the lower-mantle oxide magnesiowüstite (Mg,Fe)O. Upon reaching high-spin low-spin transition of Fe2+ about 60 GPa, we observed enhanced in mid- and near-infrared spectral range, whereas visible-ultraviolet was reduced. The changes are contrast prediction attributed d-d orbital charge transfer ion. results indicate that (Mg,Fe)O will exhibit lower radiative thermal conductivity than (Mg,Fe)O, which needs...
The discovery of iron-based superconductors (FeSCs), with the highest transition temperature (Tc) up to 55 K, has attracted worldwide research efforts over past ten years. So far, all these FeSCs structurally adopt FeSe-type layers a square iron lattice and superconductivity can be generated by either chemical doping or external pressure. Herein, we report observation in an honeycomb via pressure-driven spin-crossover. Under compression, layered FePX3 (X = S, Se) simultaneously undergo large...
The only known compound of sodium and hydrogen is archetypal ionic NaH. Application high pressure to promote states with higher atomic coordination, but extensive searches for polyhydrides unusual stoichiometry have had limited success in spite several theoretical predictions. Here we report the first observation formation Na (NaH3 NaH7) above 40 GPa 2,000 K. We combine synchrotron X-ray diffraction Raman spectroscopy a laser-heated diamond anvil cell random structure searching, which both...
Recent reports of the superconductivity in hydrides two different families (covalent lattice, as SH3 and clathrate-type H-cages containing La Y atoms, LaH10 YH6) have revealed new high-Tc materials with Tc’s near room temperature values. These findings confirm earlier expectations that may very high due to fact light H atoms vibrational frequencies, leading Tc values within conventional Bardeen–Cooper–Schrieffer phonon mechanism superconductivity. However, is pointed out by Ashcroft, it...