Superior Superconducting Properties Realized in Quaternary La-Y-Ce Hydrides at Moderate Pressures

The recent revolution in the superconductivity field stems from hydride superconductors. Multicomponent hydrides provide a crucial platform for tracking high-temperature superconductors. Besides high superconducting transition temperature (Tc), achieving both giant upper critical magnetic field [μ0Hc2(0)] and high critical current density [Jc(0)] is also key to the latent potential of the application for hydride superconductors. In this work, we have successfully synthesized quaternary La-Y-Ce hydrides with excellent properties under moderate pressure by using the concept of "entropy engineering." The obtained temperature dependence of the resistance provides evidence for the superconductivity of Fm3m-(La,Y,Ce)H10, with the maximum Tc ∼ 190 K (at 112 GPa). Notably, Fm3m-(La,Y,Ce)H10 boasts exceptional properties: μ0Hc2(0) reaching 292 T and Jc(0) surpassing 4.61 × 107 A/cm2. Compared with the binary LaH10/YH10, we find that the Fm3m structure in (La,Y,Ce)H10 can be stable at relatively low pressures (112 GPa). These results indicate that multicomponent hydrides can significantly enhance the superconducting properties and regulate stabilizing pressure through the application of "entropy engineering." This work stimulates the experimental exploration of multihydride superconductors and also provides a reference for the search of room-temperature superconductors in more diversified hydride materials in the future.

Effects of reprogrammed splenic CD8+ T-cells in vitro and in mice with spontaneous metastatic Lewis lung carcinoma

BACKGROUND

Metastatic disease is a major and difficult-to-treat complication of lung cancer. Considering insufficient effectiveness of existing therapies and taking into account the current problem of lung cancer chemoresistance, it is necessary to continue the development of new treatments.

METHODS

Previously, we have demonstrated the antitumor effects of reprogrammed CD8+ T-cells (rCD8+ T-cells) from the spleen in mice with orthotopic lung carcinoma. Reprogramming was conducted by inhibiting the MAPK/ERK signalling pathway through MEKi and the immune checkpoint PD-1/PD-L1. Concurrently, CD8+ T-cells were trained in Lewis lung carcinoma (LLC) cells. We suggested that rCD8+ T-cells isolated from the spleen might impede the development of metastatic disease.

RESULTS

The present study has indicated that the reprogramming procedure enhances the survival and cytotoxicity of splenic CD8+ T-cells in LLC culture. In an LLC model of spontaneous metastasis, splenic rCD8 + T-cell therapy augmented the numbers of CD8+ T-cells and CD4+ T-cells in the lungs of mice. These changes can account for the partial reduction of tumors in the lungs and the mitigation of metastatic activity.

CONCLUSIONS

Our proposed reprogramming method enhances the antitumor activity of CD8+ T-cells isolated from the spleen and could be valuable in formulating an approach to treating metastatic disease in patients with lung cancer.

Diverse high-pressure chemistry in Y-NH3BH3 and Y-paraffin oil systems

The yttrium-hydrogen system has gained attention because of near-ambient temperature superconductivity reports in yttrium hydrides at high pressures. We conducted a study using synchrotron single-crystal x-ray diffraction (SCXRD) at 87 to 171 GPa, resulting in the discovery of known (two YH3 phases) and five previously unknown yttrium hydrides. These were synthesized in diamond anvil cells by laser heating yttrium with hydrogen-rich precursors-ammonia borane or paraffin oil. The arrangements of yttrium atoms in the crystal structures of new phases were determined on the basis of SCXRD, and the hydrogen content estimations based on empirical relations and ab initio calculations revealed the following compounds: Y3H11, Y2H9, Y4H23, Y13H75, and Y4H25. The study also uncovered a carbide (YC2) and two yttrium allotropes. Complex phase diversity, variable hydrogen content in yttrium hydrides, and their metallic nature, as revealed by ab initio calculations, underline the challenges in identifying superconducting phases and understanding electronic transitions in high-pressure synthesized materials.

High temperature decomposition of polymeric carbon monoxide at pressures up to 120 GPa

While polymeric carbon monoxide (pCO) has been experimentally found to remain amorphous and undecomposed at room temperature up to 50 GPa, the question of whether crystalline counterparts of it can be obtained naturally raises. From different computational studies, it can be inferred that either the crystallization of amorphous pCO (a-pCO) or its decomposition into a mixture of CxOy suboxides (x > y) or carbon and CO2 may occur. In this study, we report experimental investigations of the high temperature (700-4000 K) transformation of a-pCO in the 47-120 GPa pressure range, conducted by x-ray diffraction in laser heated diamond anvil cells. Our results show the formation of no crystalline phases other than CO2 phase V, thus indicating the decomposition of the pristine a-pCO into CO2 and, likely, a mixture of amorphous CxOy suboxides and amorphous carbon hardly detectable at extreme conditions. These results support the theoretical picture of the pCO decomposition. We also show that the pressure-temperature kinetic border for this decomposition is very steep, thus indicating a strongly pressure-dependent kinetic barrier.

On the identification of hyperhydrated sodium chloride hydrates, stable at icy moon conditions

Sodium chloride is expected to be found on many of the surfaces of icy moons like Europa and Ganymede. However, spectral identification remains elusive as the known NaCl-bearing phases cannot match current observations, which require higher number of water of hydration. Working at relevant conditions for icy worlds, we report the characterization of three "hyperhydrated" sodium chloride (SC) hydrates, and refined two crystal structures [2NaCl·17H2O (SC8.5); NaCl·13H2O (SC13)]. We found that the dissociation of Na+ and Cl- ions within these crystal lattices allows for the high incorporation of water molecules and thus explain their hyperhydration. This finding suggests that a great diversity of hyperhydrated crystalline phases of common salts might be found at similar conditions. Thermodynamic constraints indicate that SC8.5 is stable at room pressure below 235 K, and it could be the most abundant NaCl hydrate on icy moon surfaces like Europa, Titan, Ganymede, Callisto, Enceladus, or Ceres. The finding of these hyperhydrated structures represents a major update to the H2O-NaCl phase diagram. These hyperhydrated structures provide an explanation for the mismatch between the remote observations of the surface of Europa and Ganymede and previously available data on NaCl solids. It also underlines the urgent need for mineralogical exploration and spectral data on hyperhydrates at relevant conditions to help future icy world exploration by space missions.

Host-Guest Hydrogen Bonding in High-Pressure Acetone Clathrate Hydrates: In Situ Single-Crystal X-ray Diffraction Study

The phenomenon of host-guest hydrogen bonding in clathrate hydrate crystal structures and its effect on physical and chemical properties have become subjects of extensive research. Hydrogen bonding has been studied for cubic (sI and sII) and hexagonal (sH) binary clathrates, while it has not been addressed for clathrate structures that exist at elevated pressures. Here, four acetone hydrate clathrates have been grown at high-pressure and low-temperature conditions. In situ single-crystal X-ray diffraction revealed that the synthesized phases possess already known trigonal (sTr), orthorhombic (sO), and tetragonal (sT) crystal structures as well as a previously unknown orthorhombic structure, so-called sO-II. Only sO and sII have previously been reported for acetone clathrates. Structural analysis suggests that acetone oxygens are hydrogen-bonded to the closest water oxygens of the host frameworks. Our discoveries show that clathrate hydrates hosting polar molecules are not as exotic as previously thought and could be stabilized at high-pressure conditions through hydrogen bonding.

Edge-sharing BO4 tetrahedra and penta-coordinated silicon in the high-pressure modification of NaBSi3O8

High-pressure modification of NaBSi3O8 results in the first example of a borosilicate compound containing edge-sharing BO4 tetrahedra and SiO5 polyhedra.

Laser heating system at the Extreme Conditions Beamline, P02.2, PETRA III

A laser heating system for samples confined in diamond anvil cells paired with in situ X-ray diffraction measurements at the Extreme Conditions Beamline of PETRA III is presented. The system features two independent laser configurations (on-axis and off-axis of the X-ray path) allowing for a broad range of experiments using different designs of diamond anvil cells. The power of the continuous laser source can be modulated for use in various pulsed laser heating or flash heating applications. An example of such an application is illustrated here on the melting curve of iron at megabar pressures. The optical path of the spectroradiometry measurements is simulated with ray-tracing methods in order to assess the level of present aberrations in the system and the results are compared with other systems, that are using simpler lens optics. Based on the ray-tracing the choice of the first achromatic lens and other aspects for accurate temperature measurements are evaluated.

Unconventional Route to High-Pressure and -Temperature Synthesis of GeSn Solid Solutions

Ge and Sn are unreactive at ambient conditions. Their significant promise for optoelectronic applications is thus largely confined to thin film investigations. We sought to remove barriers to reactivity here by accessing a unique pressure, 10 GPa, where the two elements can adopt the same crystal structure (tetragonal, I4₁/amd) and exhibit compatible atomic radii. The route to GeSn solid solution, however, even under these directed conditions, is different. Reaction upon heating at 10 GPa occurs between unlike crystal structures (Ge, Fd3m and Sn, I4/mmm), which also have highly incompatible atomic radii. They should not react, but they do. A reconstructive transformation of I4/mmm into the I4₁/amd solid solution then follows. The new tetragonal GeSn solid solution (I4₁/amd a = 5.280(1) Å, c = 2.915(1) Å, Z = 4 at 9.9 GPa and 298 K) also constitutes the structural and electronic bridge between 4-fold and newly prepared 8-fold coordinated alloy cubic symmetries. Furthermore, using this high-pressure route, bulk cubic diamond-structured GeSn alloys can now be obtained at ambient pressure. The findings here remove confining conventional criteria on routes to synthesis. This opens innovative avenues to advanced materials development.

An Unexpected Cubic Symmetry in Group IV Alloys Prepared Using Pressure and Temperature

The cubic diamond (Fd3‾m) group IVA element Si has been the material driver of the electronics industry since its inception. We report synthesis of a new cubic (Im3‾m) group IVA material, a GeSn solid solution, upon heating Ge and Sn at pressures from 13 to 28 GPa using double‐sided diamond anvil laser‐heating and large volume press methods. Both methods were coupled with in situ angle dispersive X‐ray diffraction characterization. The new material substantially enriches the seminal group IVA alloy materials landscape by introducing an eightfold coordinated cubic symmetry, which markedly expands on the conventional tetrahedrally coordinated cubic one. This cubic solid solution is formed, despite Ge never adopting the Im3‾m symmetry, melting inhibiting subsequent Im3‾m formation and reactant Ge and Sn having unlike crystal structures and atomic radii at all these pressures. This is hence achieved without adherence to conventional formation criteria and routes to synthesis. This advance creates fertile avenues for new materials development.

Polymorphs of the Gadolinite-Type Borates ZrB2 O5 and HfB2 O5 Under Extreme Pressure

Based on the results from previous high‐pressure experiments on the gadolinite‐type mineral datolite, CaBSiO₄(OH), the behavior of the isostructural borates β‐HfB₂O₅ and β‐ZrB₂O₅ have been studied by synchrotron‐based in situ high‐pressure single‐crystal X‐ray diffraction experiments. On compression to 120 GPa, both borate layer‐structures are preserved. Additionally, at ≈114 GPa, the formation of a second phase can be observed in both compounds. The new high‐pressure modification γ‐ZrB₂O₅ features a rearrangement of the corner‐sharing BO₄ tetrahedra, while still maintaining the four‐ and eight‐membered rings. The new phase γ‐HfB₂O₅ contains ten‐membered rings including the rare structural motif of edge‐sharing BO₄ tetrahedra with exceptionally short B−O and B⋅⋅⋅B distances. For both structures, unusually high coordination numbers are found for the transition metal cations, with ninefold coordinated Hf⁴⁺, and tenfold coordinated Zr⁴⁺, respectively. These findings remarkably show the potential of cold compression as a low‐energy pathway to discover metastable structures that exhibit new coordinations and structural motifs.

High-Pressure Polymeric Nitrogen Allotrope with the Black Phosphorus Structure

Studies of polynitrogen phases are of great interest for fundamental science and for the design of novel high energy density materials. Laser heating of pure nitrogen at 140 GPa in a diamond anvil cell led to the synthesis of a polymeric nitrogen allotrope with the black phosphorus structure, bp-N. The structure was identified in situ using synchrotron single-crystal x-ray diffraction and further studied by Raman spectroscopy and density functional theory calculations. The discovery of bp-N brings nitrogen in line with heavier pnictogen elements, resolves incongruities regarding polymeric nitrogen phases and provides insights into polynitrogen arrangements at extreme densities.

Nitride Spinel: An Ultraincompressible High-Pressure Form of BeP2 N4

Owing to its outstanding elastic properties, the nitride spinel γ‐Si₃N₄ is of considered interest for materials scientists and chemists. DFT calculations suggest that Si₃N₄‐analog beryllium phosphorus nitride BeP₂N₄ adopts the spinel structure at elevated pressures as well and shows outstanding elastic properties. Herein, we investigate phenakite‐type BeP₂N₄ by single‐crystal synchrotron X‐ray diffraction and report the phase transition into the spinel‐type phase at 47 GPa and 1800 K in a laser‐heated diamond anvil cell. The structure of spinel‐type BeP₂N₄ was refined from pressure‐dependent in situ synchrotron powder X‐ray diffraction measurements down to ambient pressure, which proves spinel‐type BeP₂N₄ a quenchable and metastable phase at ambient conditions. Its isothermal bulk modulus was determined to 325(8) GPa from equation of state, which indicates that spinel‐type BeP₂N₄ is an ultraincompressible material.

High-pressure synthesis of ultraincompressible hard rhenium nitride pernitride Re2(N2)(N)2 stable at ambient conditions

High-pressure synthesis in diamond anvil cells can yield unique compounds with advanced properties, but often they are either unrecoverable at ambient conditions or produced in quantity insufficient for properties characterization. Here we report the synthesis of metallic, ultraincompressible (K₀ = 428(10) GPa), and very hard (nanoindentation hardness 36.7(8) GPa) rhenium nitride pernitride Re₂(N₂)(N)₂. Unlike known transition metals pernitrides Re₂(N₂)(N)₂ contains both pernitride N₂^4- and discrete N^3- anions, which explains its exceptional properties. Re₂(N₂)(N)₂ can be obtained via a reaction between rhenium and nitrogen in a diamond anvil cell at pressures from 40 to 90 GPa and is recoverable at ambient conditions. We develop a route to scale up its synthesis through a reaction between rhenium and ammonium azide, NH₄N₃, in a large-volume press at 33 GPa. Although metallic bonding is typically seen incompatible with intrinsic hardness, Re₂(N₂)(N)₂ turned to be at a threshold for superhard materials.

Boron Phosphorus Nitride at Extremes: PN6 Octahedra in the High-Pressure Polymorph β-BP3 N6

The high-pressure behavior of non-metal nitrides is of special interest for inorganic and theoretical chemistry as well as materials science, as these compounds feature intriguing elastic properties. The double nitride α-BP₃ N₆ was investigated by in situ single-crystal X-ray diffraction (XRD) upon cold compression to a maximum pressure of about 42 GPa, and its isothermal bulk modulus at ambient conditions was determined to be 146(6) GPa. At maximum pressure the sample was laser-heated, which resulted in the formation of an unprecedented high-pressure polymorph, β-BP₃ N₆ . Its structure was elucidated by single-crystal XRD, and can be described as a decoration of a distorted hexagonal close packing of N with B in tetrahedral and P in octahedral voids. Hence, β-BP₃ N₆ is the first nitride to contain PN₆ octahedra, representing the much sought-after proof of principle for sixfold N-coordinated P that has been predicted for numerous high-pressure phases of nitrides.

New dynamic diamond anvil cells for tera-pascal per second fast compression x-ray diffraction experiments

Fast compression experiments performed using dynamic diamond anvil cells (dDACs) employing piezoactuators offer the opportunity to study compression-rate dependent phenomena. In this paper, we describe an experimental setup which allows us to perform time-resolved x-ray diffraction during the fast compression of materials using improved dDACs. The combination of the high flux available using a 25.6 keV x-ray beam focused with a linear array of compound refractive lenses and the two fast GaAs LAMBDA detectors available at the Extreme Conditions Beamline (P02.2) at PETRA III enables the collection of x-ray diffraction patterns at an effective repetition rate of up to 4 kHz. Compression rates of up to 160 TPa/s have been achieved during the compression of gold in a 2.5 ms fast compression using improved dDAC configurations with more powerful piezoactuators. The application of this setup to low-Z compounds at lower compression rates is described, and the high temporal resolution of the setup is demonstrated. The possibility of applying finely tuned pressure profiles opens opportunities for future research, such as using oscillations of the piezoactuator to mimic propagation of seismic waves in the Earth.

A closer look into close packing: pentacoordinated silicon in a high-pressure polymorph of danburite

Due to their high technological and geological relevance, silicates are one of the most studied classes of inorganic compounds. Under ambient conditions, the silicon in silicates is almost exclusively coordinated by four oxygen atoms, while high-pressure treatment normally results in an increase in the coordination from four- to sixfold. Reported here is a high-pressure single-crystal X-ray diffraction study of danburite, CaB2Si2O8, the first compound showing a step-wise transition of Si coordination from tetrahedral to octahedral through a trigonal bipyramid. Along the compression, the Si2O7 groups of danburite first transform into chains of vertice-sharing SiO5 trigonal bipyramids (danburite-II) and later into chains of edge-sharing SiO6 octahedra (danburite-III). It is suggested that the unusual formation of an SiO5 configuration is a consequence of filling up the pentacoordinated voids in the distorted hexagonal close packing of danburite-II.

Structural and Magnetic Transitions in CaCo3V4O12 Perovskite at Extreme Conditions

We investigated the structural, vibrational, magnetic, and electronic properties of the recently synthesized CaCo₃V₄O₁₂ double perovskite with the high-spin (HS) Co²⁺ ions in a square-planar oxygen coordination at extreme conditions of high pressures and low temperatures. The single-crystal X-ray diffraction and Raman spectroscopy studies up to 60 GPa showed a conservation of its cubic crystal structure but indicated a crossover near 30 GPa. Above 30 GPa, we observed both an abnormally high "compressibility" of the Co-O bonds in the square-planar oxygen coordination and a huge anisotropic displacement of HS-Co²⁺ ions in the direction perpendicular to the oxygen planes. Although this effect is reminiscent of a continuous HS → LS transformation of the Co²⁺ ions, it did not result in the anticipated shrinkage of the cell volume because of a certain "stiffing" of the bonds of the Ca and V cations. We verified that the oxidation states of all the cations did not change across this crossover, and hence, no charge-transfer effects were involved. Consequently, we proposed that CaCo₃V₄O₁₂ could undergo a phase transition at which the large HS-Co²⁺ ions were pushed out of the oxygen planes because of lattice compression. The antiferromagnetic transition in CaCo₃V₄O₁₂ at 100 K was investigated by neutron powder diffraction at ambient pressure. We established that the magnetic moments of the Co²⁺ ions were aligned along one of the cubic axes, and the magnetic structure had a 2-fold periodicity along this axis, compared to the crystallographic one.