New Publications

https://doi.org/10.1116/6.0003772

Using the methods of atomic force and electron microscopy and the magneto-optical Kerr effect, the role of the interface, roughness, and thickness of the magnetic layer in the temperature-dependent magnetic properties of thin Al₂O₃–Co films with a naturally oxidized cobalt surface was studied. The layers were deposited by magnetron sputtering. The thickness of the cobalt layer varied from 2 to 100 nm. For the first time, the dependences of coercive forces and exchange displacements on the thickness of the cobalt film in the temperature range from 80 to 300 K were obtained and analyzed. The contribution to the coercive force and exchange displacement from the oxidized cobalt surface increases as the temperature decreases below 160 K. The magnitude of the contribution depends on the base material on which the cobalt film is deposited and is maximum for a cobalt film with a thickness of ∼20 nm in the Al₂O₃/Co structure. A weakly magnetic layer was found at the Al₂O₃/Co interface. The behavior of the exchange bias in this layer is similar to the behavior of a ferromagnetic Co core with a naturally oxidized CoO shell. The thickness of this layer depends on the speed and order of deposition of the layers. When the order of deposition of layers (Co/Al₂O₃) changes, the behavior of the exchange displacement of the interface becomes similar to that observed in the ferromagnet/antiferromagnet system. That is, when the deposition order changes, the value of the exchange shift changes sign when the cobalt layer thickness is below 10 nm.

DOI 10.1088/1361-648X/ad6e48

Magnetic circular dichroism (MCD) spectroscopy for manganite films of various compositions and morphologies has been studied in the range of 1.2–3.7 eV. The primary focus was on the temperature behavior of the MCD spectra, as well as the magnetization and resistivity of the films. The data obtained were analyzed in comparison with magneto-optical spectroscopy of the Kerr rotation (KR) on both single crystal and thin film of manganites. It has been established that the MCD response at 2.3 eV is typical for manganites transitioning into a conducting state. Consequently, it reflects a change in the band structure of the material. This response is also observed in the KR spectrum of manganites in the range 2.3–2.6 eV below the metal-insulator transition temperature. These findings complement the understanding of the electronic structure of manganites in general. Moreover, they also provide a basis for the search for new functional materials.

 https://elib.sfu-kras.ru/handle/2311/152994

In this work, a study of iron and silver nanoparticles was carried out by Raman spectroscopy. The spectra were obtained by changing the temperature. The positions of individual spectral lines were found to determine the presence or absence of second-order phase transitions. Based on the data on the shift of spectral lines, one can also draw a conclusion about the stability of the objects of study under changing external conditions and how this affects changes in the suspensions in which they are included. Absorption coefficients were measured, and the sizes of the studied nanoparticles in aqueous suspensions were determined

https://doi.org/10.1016/j.jallcom.2024.176188

Na_0.5Bi_0.5TiO₃ (NBT)-based ceramics exhibit significant potential as energy storage dielectric materials due to their high maximum polarization (P_max). However, their limited energy storage density significantly restricts their practical applications. To address this, this study optimizes the dielectric energy storage characteristics of lead-free relaxor ferroelectric ceramics based on 0.91Na_0.5Bi_0.5TiO₃-0.09 K_0.7La_0.1NbO₃ (NBT-KLN) by incorporating Sr_0.7Bi_0.2TiO₃ (SBT) relaxor additives. The introduction of SBT helps maintain large polarization and induces local disorderly fields, promoting the formation of polar nanoregions. Subsequently, a viscous polymer processing (VPP) technique was employed to reduce defects and enhance density, markedly improving the breakdown strength (BDS). The findings indicate that the BDS of the optimized 0.30SBT (VPP) ceramics increased to 440 kV/cm, while achieving a high energy storage efficiency (η) of 78 % and an elevated energy storage density (W_rec) of 6.29 J/cm³. Additionally, the 0.30SBT (VPP) ceramics demonstrate excellent temperature stability across a broad temperature range from 30 to 120 °C, making them ideal for long-term operation in variable environments. This study demonstrates superior results compared to previous research, thereby opening up new avenues for developing novel lead-free relaxor ferroelectric ceramics with superior energy storage characteristics.

https://pubs.acs.org/doi/abs/10.1021/acs.cgd.4c00582

Single crystals of Co₂AlBO₅ were synthesized using flux. The structural, magnetic, and electrical properties have been studied, with emphasis on cationic disorder effects. The Al³⁺ and Co²⁺ ions share four symmetry inequivalent sites. Large amplitudes of the displacement parameters for the M2 and M4 metal sites and the O4 oxygen site were found. The compound exhibits two magnetic transitions at T₁ = 41 K and T₂ = 20 K and shows a high crystallographic anisotropy. The random cationic distribution induces magnetic softness and an increase in electrical resistivity. The sources of the cationic disorder and the approach for controlling it are discussed.

https://pubs.acs.org/doi/full/10.1021/jacs.4c06716

Gliomas remain challenging brain tumors to treat due to their infiltrative nature. Accurately identifying tumor boundaries during surgery is crucial for successful resection. This study introduces an innovative intraoperative visualization method utilizing surgical fluorescence microscopy to precisely locate tumor cell dissemination. Here, the focus is on the development of a novel contrasting agent (IR-Glint) for intraoperative visualization of human glial tumors comprising infrared-labeled Glint aptamers. The specificity of IR-Glint is assessed using flow cytometry and microscopy on primary cell cultures. In vivo effectiveness is studied on mouse and rabbit models, employing orthotopic xenotransplantation of human brain gliomas with various imaging techniques, including PET/CT, in vivo fluorescence visualization, confocal laser scanning, and surgical microscopy. The experiments validate the potential of IR-Glint for the intraoperative visualization of gliomas using infrared imaging. IR-Glint penetrates the blood–brain barrier and can be used for both intravenous and surface applications, allowing clear visualization of the tumor. The surface application directly to the brain reduces the dosage required and mitigates potential toxic effects on the patient. The research shows the potential of infrared dye-labeled aptamers for accurately visualizing glial tumors during brain surgery. This novel aptamer-assisted fluorescence-guided surgery (AptaFGS) may pave the way for future advancements in the field of neurosurgery.

https://doi.org/10.1134/S0021364024601192

Interest in hybrid quasi-one-dimensional systems with an inner semiconducting part coated with a superconductor (the so-called core/shell structure) has been grown in the last decade. Materials with a strong spin‒orbit coupling and a large g-factor (InAs, InSb) are chosen as semiconductors. Due to the proximity effect, such objects can be considered as superconducting wires, where the existence of Majorana states has been predicted. This review briefly summarizes the current experimental studies aimed at the detection of Majorana quasiparticle excitations in superconducting wires. Furthermore, prospects of using the interference geometry of devices including such wires are discussed. In particular, the coherent transport in a spatially inhomogeneous one-dimensional normal metal/superconductor/normal metal system, where normal metal wires serve as arms of an interference device, which interact with a normal metal contact, has been analyzed theoretically. It has been found that responses of Majorana and Andreev low-energy excitations of the device can be distinguished.

https://doi.org/10.1134/S0021364024601945

We calculate electronic structure and spin susceptibility dependencies on doping within the framework of a cluster perturbation theory for strongly correlated electronic systems. The change in the susceptibility with increasing doping is qualitatively consistent with the experimental data on resonant inelastic X-ray scattering and inelastic neutron scattering, as well as with the results of the calculations within the quantum Monte Carlo method.

https://doi.org/10.1016/j.commatsci.2024.113329

The unique properties of two-dimensional (2D) materials make them highly versatile for a wide range of applications. Recently, low-dimensional structures obtained from bulk non-van der Waals materials have received particular interest. Yttrium carbonate is an example of such materials which hold the potential for creating 2D structures, however, its fundamental properties have been investigated only rarely. In this work, we demonstrate the possibility of obtaining 2D yttrium carbonate with the tengerite-(Y) structure. The electronic and optical properties of both bulk and two-dimensional Y₂(CO₃)₃·2H₂O are investigated using the PBE and HSE06 functionals. While the bulk material is predicted with a bandgap of 7.06 eV at the HSE06 level, the 2D Y₂(CO₃)₃·2H₂O material possesses a bandgap of, untypically, 0.4 eV narrower than the bulk material due to surface effects and different stoichiometry. The optical properties reveal that both the bulk and 2D forms are transparent in the visible and near-UV regions positioning them as promising candidates for various optical applications including doping-induced luminescent devices.

ttps://doi.org/10.1103/PhysRevB.110.075305

We consider double perforated slabs (membranes) that support a symmetry-protected bound state in the continuum (BIC). These slabs are immersed into a liquid at room temperature. Laser excitation of the BIC generates giant optical forces that strongly affect the Brownian motion of nanoparticles in a colloidal solution. By solving of the Fokker-Planck equation we show that a single membrane can localize only larger nanoparticles. However, system of two parallel membranes can trap extremely small nanometer-sized nanoparticles by a resonant excitation of quasi-BICs, with varying intensities in each membrane

DOI: 10.1039/d4cp02289k

Successful recognition of a dynamically stable carbonitride structure revealed that unlike other planar layered structures in the case of g-C₃N₄ the stable configurations are distorted [J. Wang et al., Chem. Mater., 2017, 29(7), 2694-2707, DOI: https://doi.org/10.1021/acs.chemmater.6b02969.]. This generates interest in a detailed study of the possibilities of controlling the structure and its properties both in its pristine and heterostructure forms. Here, we present the results of the investigation of dynamically stable bulk and monolayer g-C₃N₄, and a g-C₃N₄/MoS₂ heterostructure. The bulk g-C₃N₄ was found to be an indirect band gap semiconductor exhibiting an indirect-to-direct band gap transition upon dimensionality reduction. In the case of the heterostructure, the analysis of partial density of states shows a charge transfer from nitrogen ions in g-C₃N₄ to the MoS₂ layer. The Raman spectra of bulk g-C₃N₄ are discussed in detail, and the changes occurring in the spectra upon the transition to the monolayer form and in the g-C₃N₄/MoS₂ heterostructure are demonstrated. It was found that the characteristic features of such an atomic transition can be seen in the region below 300 cm^-1 and between 700 and 800 cm^-1.

https://doi.org/10.1134/S1062873824707220

The authors study the formation of crystals of Fe-Ga oxides and Fe–Ga–Cu borates in a multicomponent flux system based on Bi₂Mo₃O₁₂–Na₂B₄O₇. The Curie–Weiss temperature (θ_CW = 289 K) and the temperature of the ferrimagnet–paramagnet phase transition (T_C = 288 K) are determined from the electron spin resonance (ESR) spectrum and the magnetization of an Fe_1.1Ga_0.9O₃ single crystal, depending on temperature. Lines of spin-wave resonance are observed in the spectrum of magnetic resonance in the ordered phase.

https://doi.org/10.1002/pssa.202400244

Thermal stability of the multilayer (Mg/NbO_x)₈₂ nanostructure and the effect of heat treatment on its electrical properties and phase composition depending on the bilayer thickness are studied. The studied (Mg/NbO_x)₈₂ samples contain 82 bilayers whose thickness varies in the range from 2.2 to 6.2 nm. The NbO_x layer thickness in the multilayers is the same (0.96 nm) in all samples, while the magnesium layers thickness is varied. It is established that the magnesium layers are either discrete (a set of nanosized particles) or continuous depending on their thickness. A metallothermic reaction occurs in (Mg/NbO_x)₈₂ multilayer nanostructures at a temperature of 430 °C: niobium oxide decomposes and the released oxygen partly oxidizes the magnesium layers. That leads to the conductive magnesium metal layers breaking and to the sharp increase of the nanostructures’ resistance by more than two orders. Despite the metallothermic reaction, the layering of the (Mg/NbO_x)₈₂ nanostructures as a whole and the presence of unoxidized magnesium inclusions remain even after heating up to 450 °C.

 https://doi.org/10.1002/chem.202402084

Complex oxides Eu₂MeO₆ (Me–Mo, W), Eu₂W₂O₉ were obtained by a solid-phase reaction between binary oxides. The thermodynamic and kinetic mechanisms of the reaction processes were established using a variety of physical-chemical methods. All compounds obtained in this work crystallize in the low-symmetry monoclinic system, forming complex framework structures, which determine a set of very valuable physical-chemical properties. Comparison of experimental Kubelka-Munk functions and DFT- calculated absorption spectra shows adequate agreement and reveals the origin of the fundamental absorption. In addition, the deficiency in DFT calculations in the part of mutual contribution of CTBs of Mo−O and W−O, from one side, and Eu−O contributions, from the other side, is reported. Calculations of absorption spectra are shown to be superior to band structure analysis in the determination of optical band gaps. Additionally, luminescent properties of Eu₂MeO₆ and Eu₂W₂O₉ compounds were investigated. These studies provide a better understanding of the electronic and optical properties of the compounds Eu₂MeO₆ and Eu₂W₂O₉, along with their potential applications in various areas.

https://doi.org/10.1134/S1070363224060094

Using the methods of X-ray diffraction, Mössbauer spectroscopy, and temperature-programmed reduction with hydrogen, the relationship between the phase composition, structural characteristics of the phases, and the reactivity with respect to hydrogen was investigated for calcium ferrites-based catalysts. The catalyst samples were prepared via solid-state synthesis from CaO and Fe₂O₃ at 900 and 1000°C by varying the Fe₂O₃ content in the CaO–Fe₂O₃ system. The phase composition of the resultant samples corresponds to the CaO‒Ca₂Fe₂O₅, Ca₂Fe₂O₅‒CaFe₂O₄, and CaFe₂O₄‒α-Fe₂O₃ regions. In the CaO–Ca₂Fe₂O₅ samples the lattice parameters of Ca₂Fe₂O₅ and its activity with respect to hydrogen depend on the phase ratio. The activity of CaFe₂O₄ is higher in Ca₂Fe₂O₅‒CaFe₂O₄ compared to CaFe₂O₄‒α-Fe₂O₃ catalysts.https://doi.org/10.1134/S1070363224060094

https://doi.org/10.1134/S1062873824707190

Results are presented from investigating the structure of Mn_2.25Co_0.75BO₅ via powder neutron diffraction. Crystals of ludwigite Mn_2.25Co_0.75BO₅ are grown by flux method using a Bi₂Mo₃O₁₂-based solvent diluted with Na₂CO₃ carbonate. Boric acid H311BO3 is used as the boron-containing reagent. Powder neutron diffraction measurements are made at a temperature of 100 K on powder prepared by grinding grown single crystals. Rietveld studies show that the grown Mn_2.25Co_0.75BO₅ crystals belong to Pbam space group. Crystallographic sites occupied by cobalt and manganese ions are identified by analyzing powder neutron diffractograms. A bottleneck regime is observed in the temperature dependence of the EPR spectra.

https://doi.org/10.1103/PhysRevB.110.045102

EuAl4 is a rare-earth intermetallic in which competing itinerant and/or indirect exchange mechanisms give rise to a complex magnetic phase diagram, including a centrosymmetric skyrmion lattice. These phenomena arise not in the tetragonal parent structure but in the presence of a charge-density wave (CDW), which lowers the crystal symmetry and renormalizes the electronic structure. Microscopic knowledge of the corresponding atomic modulations and their driving mechanism is a prerequisite for a deeper understanding of the resulting equilibrium of electronic correlations and how it might be manipulated. Here, we use synchrotron single-crystal x-ray diffraction, inelastic x-ray scattering, and lattice-dynamics calculations to clarify the origin of the CDW in EuAl4. We observe a broad softening of a transverse acoustic phonon mode that sets in well above room temperature and, at 𝑇CDW=142 K, freezes out in an atomic displacement mode described by the superspace group 𝐼⁢𝑚⁡𝑚⁡𝑚⁡(00⁢𝛾)⁢𝑠⁢00. In the context of previous work, our observation is a clear confirmation that the CDW in EuAl4 is driven by electron-phonon coupling. This result is relevant for a wider family of BaAl4 and ThCr2⁢Si2-type rare-earth intermetallics known to combine CDW instabilities and complex magnetism.

DOI 10.1209/0295-5075/ad56c3

We revisit the problem of two-terminal transport of non-interacting Fermi particles in a mesoscopic device. First, we generalize the transport problem by taking into consideration relaxation processes in contacts (which are characterized by the contact self-thermalization rate γ) and then solve it by using the master equation approach. In the limit �→0 the obtained results are shown to reproduce those of the Landauer theory. Thus, the presented analysis proves correspondence between the Landauer and master equation approaches to quantum transport —a problem which has been waiting for a solution for decades.

https://doi.org/10.1134/S1062873824706858

Water-soluble organic luminophores based on 3-(1,3-benzothiazol-2-yl)-4-hydroxybenzenesulfonic acid were studied both experimentally and by density functional theory for the first time. Because of peculiarities in chemical structure, one of them has a large Stokes shift, which results from excited state intramolecular proton transfer.

https://doi.org/10.1134/S0031918X23603025

The paper examines the impact of interparticle interactions on the superparamagnetic relaxation of ultrasmall nanoparticle ensembles, using Fe₂O₃∙nH₂O iron oxyhydroxide (ferrihydrite) nanoparticles as an example. Two samples were analyzed: ferrihydrite of biogenic origin (with an average particle size of ⟨�⟩ ≈ 2.7 nm) with a natural organic shell, and a sample (with ⟨�⟩ ≈ 3.5 nm) that underwent low-temperature annealing, during which the organic shell was partially removed. The DC and AC magnetic susceptibilities (χ′(T), χ′′(T)) in a small magnetic field in the superparamagnetic (SPM) blocking region of the nanoparticles were measured. The results show that an increase in interparticle interactions leads to an increase in the SPM blocking temperature from 28 to 52 K according to DC magnetization data. It is shown that below the SPM blocking temperature, magnetic interactions of nanoparticles lead to the formation of a collective state similar to spin glass in bulk materials. The scaling approach reveals that the dynamics of correlated magnetic moments on the particle surface slow down with increasing interparticle interactions. Simulation of χ′′(T) dependence has shown that the dissipation of magnetic energy occurs in two stages. The first stage is directly related to the blocking of the magnetic moment of nanoparticles, while the second stage reflects the spin-glass behavior of surface spins and strongly depends on the strength of interparticle interactions.

https://doi.org/10.1134/S0031918X24600088

The study investigates carbon-containing coatings of 3d-metals (Ni, Co, Fe) produced by chemical deposition method using arabinogalactan. The coatings were analyzed using X-ray diffraction, FMR, and M(H) magnetometry. Measurement of M(H) in plane and perpendicular to the plane of the magnetic coatings allowed determining the distribution of demagnetizing factor in the studied coatings. The obtained distributions of the demagnetizing factor were used to analyze the angular dependences of the ferromagnetic resonance field. The values of magnetization and perpendicular anisotropy field were estimated. The paper illustrates the effect of texture on the magnetic parameters.

https://doi.org/10.1002/andp.202400120

Light diffraction is studied numerically and experimentally on a double fork-shaped grating representing a periodic grating containing two spaced dislocations. The spatial dynamics of the phase singularities (optical vortices) has been investigated as a function of dislocation parameters. Produced optical vortices affect each other while propagating in a free space. For dislocations of the same topological charge, the propagation trajectories and their transverse displacement coordinates depend on the dislocation spacing, and the larger the dislocation spacing, the smaller the relative displacement of the optical vortices and the smaller their trajectory curvatures. For oppositely charged dislocations, three types of spatial behavior of optical vortices are found. The numerical results agree well with the experimental data.

https://doi.org/10.1016/j.ica.2024.122310

Acetate complexes of rare earth elements are extensively studied compounds known for their diverse properties and potential applications and lanthanum acetate hydrate is commercially available. In this work, a powdered anhydrous lanthanum acetate (La(CH₃COO)₃) sample was prepared by dissolving lanthanum oxide (La₂O₃) in an excess of acetic acid (CH₃COOH) and distilled water (H₂O), followed by direct evaporation at 150 °C. The decomposition of La(CH₃COO)₃ was studied, showing initiation around 300 °C and conclusion at ≥700 °C, with four distinct thermal events (I–IV) of mass loss. Gas phase identification revealed acetone and carbon dioxide as decomposition products, indicating pyrolytic decarboxylation. The final thermal effect (IV) is linked to the decomposition of La₂O₂CO₃ to La₂O₃. The DFT refinement of atomic coordinates of hydrogen atoms, which were unavailable from experiment, was successfully performed. Obtained structural data was checked using vibrational spectroscopy method. The calculated electronic band structure of La(CH₃COO)₃ indicates it as an indirect wide band gap material with values of direct transition close to indirect. The optical bandgap is found to be 5.49 eV, suggesting that the charge transfer in La(CH₃COO)₃ can be optically activated with wavelengths shorter than 226 nm, which falls within the deep UV (DUV) region.

https://doi.org/10.1134/S2075113324700400

By the example of α-Fe₂O₃ hematite, 5Fe₂O₃⋅9H₂O ferrihydrite, and γ-Fe₂O₃ maghemite powders, a microwave-radiation-induced powder system temperature growth ΔT_max of several degrees has been measured in the ferromagnetic resonance mode at a frequency of 8.9 GHz. The powders heat up the most in the external field H coinciding with the ferromagnetic resonance field. The value of the ΔT_max effect depends on the magnetization of a powder material. The results obtained allow us to propose a new magnetic hyperthermia method for biomedical applications.

 https://doi.org/10.3390/magnetochemistry10070047

The generally accepted model of the magnetic structure of an iron oxide core–shell nanoparticle includes a single-domain magnetically ordered core surrounded by a layer with a frozen spin disorder. Due to the exchange coupling between the shell and core, the spin disorder should lead to nonuniform magnetization in the core. Suppression of this inhomogeneity by an external magnetic field causes the nonlinear behavior of the magnetization as a function of the field in the region of the approach to magnetic saturation. The equation proposed to describe this effect is tested using a micromagnetic simulation. Analysis of the approach to magnetic saturation of iron oxide nanoparticles at different temperatures using this equation can be used to estimate the temperature evolution of the core–shell coupling energy and the size of the uniformly magnetized nanoparticle core and the temperature behavior of this size.

https://pubs.acs.org/doi/full/10.1021/acs.chemmater.4c01205

Negative-thermal-expansion (NTE) materials violate the common knowledge of “thermal expansion and cold contraction” in solids and embrace various physical mechanisms. In most phonon-driven NTE materials, an open-framework structure is necessary to accommodate the spatially anisotropic phonon excitations of the bridged atoms, but such a structural feature may result in structural instability at a high temperature. Herein, we focus on γ-LiBO₂ with a closed-framework diamond-like structure and identify its uniaxial NTE behavior over the largest temperature range (100−850 K) among this structural family. As the temperature increases, the synergetic structural modification of the constituent structural groups, i.e., the stretching and bending of the Li−O bonds in floppy [LiO₄] and the tension or rotation in the [BO₄] group, accounts for NTE along the c-axis. Our study unveils that, apart from the anisotropic phonon excitations of individual atoms, the preferred phonon excitations of structural groups are also able to generate NTE, which would update the understanding of the NTE mechanism and guide the further exploration of phonon-driven NTE materials.

https://doi.org/10.1063/5.0206742

The properties of charge transfer plasmons (CTPs) in periodic metallic nanoparticle arrays (PMNPAs) on the single-layer graphene surface are studied within a computationally efficient original hybrid quantum-classical model. The model is based on the proven assumption that the carrier charge density in doped graphene remains unchanged under plasmon oscillations. Calculated CTP frequencies for two PMNPA geometries are shown to lie within the THz range and to be factorized, i.e., presented as a product of two independent factors determined by the graphene charge density and the PMNPA geometry. Equations are derived for describing the CTP frequencies and eigenvectors, i.e., oscillating nanoparticle charge values. It is shown that the CTP plasmons having a band structure containing a wave vector and a band number, like to phonons in periodic media, can be divided into an acoustic mode and optical CTP modes. For the acoustic modes, the CTP group velocity tends to zero at �→0⁠, but reaches a value of ∼�Fermi in graphene inside the Brillouin zone, while for the optical modes, the group velocity dispersion is extremely weak, although their energy is higher than the acoustic plasmon energies. It is shown that the calculated dependence of CTP frequencies on the carrier concentration in graphene is in good agreement with experimental data. We believe that the proposed model can help in designing various graphene-based terahertz nanoplasmonic devices of complex geometry due to very high computational efficiency.

https://doi.org/10.1016/j.jeurceramsoc.2024.116769

The paper presents the results of detailed studies of thermal expansion of solid solutions (1-x)Na1/2Bi1/2TiO3-xBaTiO3 with x=0.04-0.97 in the temperature range from 100 to 900 K. A change in chemical pressure associated with the complex cationic substitution, (Na1/2Bi1/2)2+→ Ba2+, result in a very rapid decrease in the temperatures of the transformation �4��→�2��→�3� below 100 K which are characteristic of BaTiO3. Significant features in the behavior of thermal expansion were observed near two triple points in the �−� phase diagram where the phases ��3̄�, �4��, �4�� (x≈0.15-0.20) and �4��, �4��, �3� (x≈0,06) coexist, allow the studied solid solutions to be divided into three groups. The relationship between the effects of internal chemical pressure and external hydrostatic one is discussed. By analyzing the thermodynamic potential, the root-mean-square polarization �� is determined, which increases by about 16% with a decrease in the BT content from 0.97 to 0.4.

https://doi.org/10.1016/j.saa.2024.124801

The study of Na-carbonates stability and their transformations in aqueous carbonate fluid under high P–T conditions is relevant from the point of view of the understanding geochemical processes of the Na-assisted carbon circulation in the Earth’s crust and subduction zones. In situ Raman study of Na-bearing carbonate-water-Fe-metal system in diamond anvil cell (DAC) at high P–T conditions revealed that carbonates decompose with abiogenic formation of formates and other organic compounds that differs from behavior of carbonates in dry system. XRD and FTIR methods have been used additionally to determine the phase composition. Na-bearing carbonates (nahcolite NaHCO3, shortite Na2Ca2(CO3)3 and cancrinite Na7Ca[(CO3)_1.5Al6Si6O₂₄]⋅2H2O) in aqueous fluid decompose to form simple carbonates and formates (as dominant organic molecules) at moderate P–T parameters (above ∼0.2 GPa, 200 °C). Our experimental results directly confirm the hypothesis of Horita and Berndt (Science, 1999) about possible yield of organic formates in the carbonate-water-metal system.

Nahcolite NaHCO3 in aqueous fluid in the presence of Fe metal decomposes into anhydrous phases: natrite �-Na2CO3, siderite, magnetite (due to dissolution of Fe steel gasket), Na-formate and likely organic molecular crystalline solvate of Na-formate and methyl formate. Shortite decays into anhydrous phases: aragonite CaCO3, Na-Ca-formates and an amorphous phase. Cancrinite decomposes to unidentified carbonate-alumonosilicate phases, Na-Ca-formates and unknown organic molecular crystal. Magnetite is also formed in this system due to dissolution of Fe steel gasket used in DAC. The present study provides a new insight in processes of abiogenic formation of organic matter from carbonates in the crust and upper mantle.

https://doi.org/10.1002/adma.202406164

The quest for artificial light sources mimicking sunlight has been a long-standing endeavor, particularly for applications in anticounterfeiting, agriculture, and color hue detection. Conventional sunlight simulators are often cost-prohibitive and bulky. Therefore, the development of a series of single-phase phosphors Ca₉LiMg_1-xAl_2x/3(PO₄)₇:0.1Eu²⁺ (x = 0-0.75) with sunlight-like emission represents a welcome step towards compact and economical light source alternatives. The phosphors are obtained by an original heterovalent substitution method and emit a broad spectrum   spanning from violet to deep red. Notably, the phosphor with x = 0.5 exhibits an impressive full width at half-maximum of 330 nm. A synergistic interplay of experimental investigations and theory unveils the mechanism behind sunlight-like emission due to the local structural perturbations introduced by the heterovalent substitution of Al³⁺ for Mg²⁺, leading to a varied distribution of Eu²⁺ within the lattice. Subsequent characterization of a series of organic dyes combining absorption spectroscopy with convolutional neural network analysis convincingly demonstrates the potential of this phosphor in portable photodetection devices. Broad-spectrum light source testing empowers the model to precisely differentiate dye patterns. This points to the phosphor being ideal for mimicking sunlight. Beyond this demonstrated application, the phosphor's utility is envisioned in other relevant domains, including visible light communication and smart agriculture.