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Due to their widespread occurrence in several geological settings, omphacite inclusions could be used for elastic Raman geothermobarometry. However, the Raman scattering of complex silicate minerals entrapped in a host depends on both the chemical composition and elastic strain developed during the metamorphic pathway, which makes the task very challenging. Here, as a very first step to probe the potential of omphacite to be used as a mineral inclusion in elastic geothermobarometry, we report the pressure dependence of the Raman spectra of omphacite crystals with the same composition, approximately Jd43Di57, but having different symmetry because of the existence (P2/n) or absence (C2/c) of chemical order at the six- and eight-coordinated cation sites. The experimental results are complemented by ab initio quantum mechanical simulations on fully ordered omphacite (Jd50Di50). We demonstrate that the position of the well-resolved Raman peak near 688 cm–1, arising from Si-O-Si bond bending, is very sensitive to pressure but independent of the state of chemical order, which makes it promising to be utilized in Raman geobarometry. The width of this peak varies with chemical order but not with pressure and therefore can be used to constrain the temperature of inclusion entrapment, because the chemical order is indicative of the closure temperature of the cation-exchange reaction. However, further detailed analyses on the compositional variation of the Raman spectra of omphacite is required before considering omphacite-in-garnet systems to be suitable for Raman elastic geothermobarometry. [ABSTRACT FROM AUTHOR]

Azoles are widely used as bioactive substances, herbicides, catalysts, corrosion inhibitors, polymeric compositors, organometallic ligands, and optical elements' components. The interaction with water plays a crucial role in many applications of azoles. The objective of this study is to observe the molecular interaction and structural transformations of 1,2‐ and 1,3‐diazoles', 1,2,3‐ and 1,2,4‐triazoles' complexes with water molecules. We have selected the most valuable for application and theoretical interest azoles with different molecular structures, which have allowed us to consider the basic features of their aqueous complexes. We used the IR study method allowing to fix water intermediates in the solid phase. We have also employed the hybrid B3LYP functional DFT method with GD3BJ dispersion correction. At the cluster formation, the hydrogen atom transfer arises, providing a labile spatial arrangement of the water system. The formation of azoles' complexes with a hydronium ion having relatively low binding energy allows the reshaping of the complexes' structure at the hydrogen atom cluster‐to‐cluster transition. The complex formation is accompanied by the hydrogen atom transfer with the participation of both water and azole hydrogen atoms. This transfer provides the mobile spatial arrangement of clusters and hydrogen atom transition from donor to acceptor centers. [ABSTRACT FROM AUTHOR]

The structural, dynamical, and thermodynamic properties of zinc‐blende (ZB) mercury selenide (HgSe) and cadmium selenide (CdSe) were systematically explored using an ab initio pseudopotential approach based on the density functional theory (DFT). The optimized lattice constants are in excellent agreement with the available experimental and theoretical results. The electronic properties show semiconducting behavior with a direct bandgap of 0 and 0.36 eV for HgSe and CdSe, respectively. Also, using the linear response approach, the detailed vibration properties of HgSe and CdSe are obtained. According to the calculated phonon dispersion, it is concluded that HgSe and CdSe are dynamically stable in the ground state; several peculiarities in the dispersion curves of these materials are generally similar, but the zone‐boundary frequencies and zone‐center optical frequencies of HgSe are lower than those of CdSe. The phonon frequencies at the high‐symmetry points Γ, X, and L for HgSe and CdSe are in good agreement with the other theoretical reported. On the other hand, the dielectric properties are investigated and discussed. The results show that the dielectric tensor is diagonal, and the Born effective charge tensor is also isotropic. Finally, based on the lattice dynamical properties, we investigate the thermodynamic properties of both compounds, such as Helmholtz free energy F, internal energy E, entropy S, and specific heat Cv. The results show that HgSe and CdSe exhibit similar but slightly different behaviors in terms of its thermodynamic properties, which is expected because the atoms Hg and Cd are in the same group and exhibit a different atom mass. Most of the results presented in this study are novel and should provide a useful reference for future studies. [ABSTRACT FROM AUTHOR]

On the one hand, Ni3-xCoxB2O6 solid solutions are promising anode materials for lithium batteries, and on the other hand, they have antiferromagnetic properties. This study examines the lattice dynamics of Ni3-xCoxB2O6 solid solutions for x = 0, 1, 2, 3 by means of quantum chemistry and Raman spectroscopy. The vibrational spectra of the compound NiCo2B2O6 have been studied using the polarized Raman spectroscopy method. Good agreement was found between the theoretical and experimental results. As expected, the largest change in frequencies was observed in the modes where the vibrations of the metal ion had a large amplitude. The substitution of cobalt by nickel does not lead to the appearance of soft modes. This fact indicates that the structures of the solid solutions are stable. [ABSTRACT FROM AUTHOR]

[Display omitted] • Driving mechanism of self-assembly pattern lithographed on water-soluble crystals. • Ion adsorption-enrichment effect induced by the SPM probes in the water menisci. • Interactions between the water-soluble crystal growth units and the SPM probes. • A lithography model to reveal the SPM probe-induced self-assembly behaviors. Water-soluble KDP (KH 2 PO 4) crystals possess excellent optical properties and are employed as frequency converters in clean fusion energy. To improve their performances, there is an immediate necessity to lithograph surface nano-patterns on them. Although the Scanning Probe Microscope (SPM) provides a promising way to achieve this purpose through the water menisci, the driving mechanisms of the lithographic behaviors have not yet been revealed. Multi-scale investigations are constructed to explore the underlying driving mechanisms. The SPM probe-induced ion diffusion-transport behaviors are investigated by molecular dynamics. The ion adsorption-enrichment mechanisms are revealed by 18 adsorption models via the ab initio. The SPM probe-induced self-assembly experiments are performed to prove the local heavy concentration. A comprehensive model is developed to describe the lithography mechanisms of the probe-induced self-assembly nano-dots on water-soluble substrates. It is interestingly found that the KDP growth units (H 2 PO 4 −) exhibit obvious adsorption-enrichment effect at 3.16 Å from the probe surface, causing local heavy concentration. The H 2 PO 4 − would spontaneously adsorb onto the probe surface, which is dominated by the Si-O bonding reactions. The nano-dots with the height of 27 ∼ 48 nm and diameter of 2.0 ∼ 2.7 μm are lithographed on the KDP substrate. The proposed model further confirms that the lithography processes are driven by the solution supersaturation, solute diffusion, and surface free energy. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) are essential to the reliable high-temperature operation of gas turbines and engines. They comprise a ceramic top coat (TC), a metallic bond coat (BC), and a superalloy substrate. Metallic BCs are common, but they require a minimal difference in the coefficient of thermal expansion (CTE) between the TC and substrate. Among ceramic materials, MAX phases have high CTE. This study reports our use of ab initio calculations to assess the suitability of MAX phases as TBCs. We model Nb-based MAX phases with 211 and 312 structures that have Al or Si at the A sites and C or N at the X sites. We use the quasi-harmonic approximation to calculate the Young's moduli and CTEs of the materials with respect to temperature. The Nb2SiN MAX phase appears as the most suitable for use as a BC between various ceramic TCs and an Inconel-718 substrate. It is predicted to be effective in relieving thermal stresses due to its high CTE of 10.882 × 10−⁶ K−1 at 1273 K. The results indicate that carbide MAX phases with high Young's modulus and low CTE should be used with caution. They may not accommodate thermal stresses as effectively, potentially leading to material failure or reduced performance. Overall, our study indicates the potential of Nb-based MAX structures for use as BCs.

Superalkalis (SAs) are exotic clusters having lower ionization energy than alkali atoms, which makes them strong reducing agents. In the quest for the reduction of diatomic molecules (X2) such as N2, O2, and H2 using Møller‐Plesset perturbation theory (MP2), we have studied their interaction with typical superalkalis such as FLi2, OLi3, and NLi4 and calculated various parameters of the resulting SA−X2 complexes. We noticed that the SA−O2 complex and its isomers possess strong ionic interaction, which leads to the reduction of O2 to O2− anion. On the contrary, there are both ionic and covalent interactions in SA−N2 complexes such that the lowest energy isomers are covalently bonded with no charge transfer from SA. Further, the interaction between SA and H2 leads to weakly bound complexes, which results in the adsorption of H2 molecules. The nature of interaction is found to be closely related to the electron affinity of diatomic molecules. These findings might be useful in the study of the activation, reduction, and adsorption of small molecules, which can be further explored for their possible applications. [ABSTRACT FROM AUTHOR]

Davemaoite, that is, CaSiO3 perovskite (CaPv), is the third most abundant phase in the lower mantle and exhibits a tetragonal‐cubic phase transition at high pressures and temperatures. The phase boundary in CaPv has recently been proposed to be close to the cold slab adiabat and cause mid‐mantle seismic wave speed anomalies (Thomson et al., 2019, https://doi.org/10.1038/s41586‐019‐1483‐x). This study utilized accurate deep‐learning‐based simulations and thermodynamic integration techniques to compute free energies at temperatures ranging from 300 to 3,000 K and pressures up to 130 GPa. Our results indicate that CaPv exhibits a single cubic phase throughout lower‐mantle conditions. This suggests that the phase diagram proposed by Thomson et al. requires revision, and mid‐mantle seismic anomalies are likely attributable to other mechanisms. Plain Language Summary: Davemaoite, also known as calcium silicate perovskite (CaPv), is one of the most abundant minerals in Earth's lower mantle. It can exist in tetragonal and cubic crystal structures, depending on the pressure and temperature conditions. Determining the crystalline phase of CaPv is important for interpreting seismic observations of the lower mantle. A recent study (Thomson et al., 2019, https://doi.org/10.1038/s41586‐019‐1483‐x) suggested that CaPv's tetragonal‐to‐cubic transition could cause mid‐mantle seismic anomalies. However, this phase transition has been a topic of debate. Previous studies have attempted to determine the phase boundary using ab initio methods. The computational cost and challenges associated with handling strong anharmonicity limited these approaches' accuracy and predictive power. In this study, we utilized deep learning and thermodynamic integration techniques to accurately compute the tetragonal to cubic phase boundary of CaPv across the lower mantle pressure range. Our results satisfactorily explain previous experimental measurements and support the notion that CaPv remains in the cubic phase across lower mantle conditions. These findings challenge the previously proposed phase diagram by Thomson et al. and suggest that mid‐mantle seismic scatterers/reflectors or large low‐shear‐velocity provinces in the lower mantle cannot be attributed to this transition in CaPv. Key Points: A deep‐learning potential is developed to accurately determine CaSiO3 perovskite (CaPv)'s tetragonal‐to‐cubic phase boundary under lower‐mantle conditionsCaPv should exhibit solely a cubic phase throughout the entire lower mantleThe tetragonal‐to‐cubic transition in CaPv is not a viable explanation for the mid‐mantle seismic scatterers/reflectors or large low‐shear‐velocity provinces [ABSTRACT FROM AUTHOR]

Marine evaporitic halite, precipitating from the advanced stage of extremely evaporated seawater, is the most common and abundant evaporitic mineral. The extent to which lithium (Li) is incorporated into evaporite halite during geological periods of massive halite deposition, and the mechanisms of incorporation, are both unknown. These are each important, however, for the quantification of the isotope effect of the evaporitic sink on δ 7 Li seawater , and for the potential use of halite as a recorder of seawater δ 7 Li. Here, new experimental data are presented for the Li fractionation factor for halite from an isothermal evaporation experiment (25 ∘C for 100 days) using marine-derived brine. The resultant solids were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to confirm the mineralogy and crystallinity of the product. Our results show that Li isotopes are not constant during the evaporation process implying that there must be a process that fractionates Li isotopes during halite precipitation. We suggest that this results from Li ionic substitution for sodium (Na) in crystalline halite, a scenario supported by ab-initio calculations, but we also show that Li within halite is predominantly present within fluid inclusions. Thus, the Li isotopic composition of halite is controlled by a mixture of Li within the fluid inclusions and Li that is incorporated into the halite crystalline structure. Overall, the brine becomes enriched in Li 7 during evaporation due to the preferential incorporation of Li 6 into chloride precipitates, and the evolution of δ 7 L i brine is controlled by the precipitated mineral assemblage. The theoretical equilibrium fractionation factor 1000ln α mineral − fluid is -7.8▪ for Li-halite (LiN a 26 C l 27) at 25 C ∘ at equilibrium, which is at the lower limit of Li isotope fractionation factors. Rayleigh fractionation models were fitted to the experimental data yielding a fractionation factor of -25▪3▪. The difference in Li isotope fractionation factor between brine and structurally bound Li may result from kinetic fractionation effects. This study presents a scenario highlighting that extensive halite deposits, formed over geological time in environments with relatively high Li concentration, could potentially impact the δ 7 Li values of seawater during that period, and place constraints on their utility as an archive for δ 7 L i seawater. [ABSTRACT FROM AUTHOR]

We investigated the electronic structure of Mg-, Si-, and Zn-doped four-faceted [001]- and [110]-oriented SnO2 nanowires using first-principles calculations based on the linear combination of atomic orbitals (LCAO) method. This approach, employing atomic-centered Gaussian-type functions as a basis set, was combined with hybrid density functional theory (DFT). Our results show qualitative agreement in predicting the formation of stable point defects due to atom substitutions on the surface of the SnO2 nanowire. Doping induces substantial atomic relaxation in the nanowires, changes in the covalency of the dopant–oxygen bond, and additional charge redistribution between the dopant and nanowire. Furthermore, our calculations reveal a narrowing of the band gap resulting from the emergence of midgap states induced by the incorporated defects. This study provides insights into the altered electronic properties caused by Mg, Si, and Zn doping, contributing to the further design of SnO2 nanowires for advanced electronic, optoelectronic, photovoltaic, and photocatalytic applications. [ABSTRACT FROM AUTHOR]

Accurate thermoelastic properties and thermal conductivity are crucial for understanding the thermal evolution of the Martian core. A fitting method based on ab initio calculated pressure‐volume‐temperature data was proposed for the formulation of the equation of state with high accuracy, by which the pressure and temperature dependent thermoelastic properties can be directly calculated by definitions. Ab initio results showed that Fe0.75S0.25 liquid under Martian core conditions was thoroughly in a magnetic state without existing spin crossover. The Fe0.75S0.25 liquid in magnetic calculations had a low thermal conductivity (21–23 W/m/K) when compared with non‐magnetic calculations at the same state. Based on Insight's estimated Martian core properties (Stähler et al., 2021, https://doi.org/10.1126/science.abi7730) and ab initio calculated properties of the Fe0.75S0.25 liquid, the scenario for the thermal evolution of the Martian core is the iron‐snow model crystallization regime. The parameter uncertainty effect on the cessation time of the dynamo and zone of iron snow was systematically analyzed. Plain Language Summary: The knowledge of the density and thermoelastic properties of the Martian core is very limited. The thermoelastic properties of Fe0.75S0.25 liquid under Martian core conditions were calculated by ab initio molecular dynamics, and the thermal evolution of the Martian core was modeled by the thermoelastic properties and the reported Insight data (Stähler et al., 2021, https://doi.org/10.1126/science.abi7730). The Fe0.75S0.25 liquid under the Martian core condition is magnetic and its thermal conductivity is 21–23 W/m/K. If the temperature at the core‐mantle boundary is higher than the core's melting temperature, the Martian core is entirely liquid with simple cooling. If the temperature is lower than the melting temperature, there exists iron snow at the top of the Martian core at present. The parameter uncertainty on the effect of the iron snow evolution of the Martian core was explored. Key Points: The thermoelastic properties were calculated by the polynomial fitted equation of stateThe Fe0.75S0.25 liquid under the Martian core condition was thoroughly in the magnetic stateThe Fe0.75S0.25 liquid in magnetic calculation had a low thermal conductivity (21–23 W/m/K) [ABSTRACT FROM AUTHOR]

Abstract Superalkalis (SAs) are exotic clusters having lower ionization energy than alkali atoms, which makes them strong reducing agents. In the quest for the reduction of diatomic molecules (X2) such as N2, O2, and H2 using Møller‐Plesset perturbation theory (MP2), we have studied their interaction with typical superalkalis such as FLi2, OLi3, and NLi4 and calculated various parameters of the resulting SA−X2 complexes. We noticed that the SA−O2 complex and its isomers possess strong ionic interaction, which leads to the reduction of O2 to O2− anion. On the contrary, there are both ionic and covalent interactions in SA−N2 complexes such that the lowest energy isomers are covalently bonded with no charge transfer from SA. Further, the interaction between SA and H2 leads to weakly bound complexes, which results in the adsorption of H2 molecules. The nature of interaction is found to be closely related to the electron affinity of diatomic molecules. These findings might be useful in the study of the activation, reduction, and adsorption of small molecules, which can be further explored for their possible applications.

The magnetic dipole and the spectroscopic quadrupole moments of the nuclear ground states in the odd-mass nickel isotopes 59−67Ni have been determined using collinear laser spectroscopy at the CERN-ISOLDE facility. They are compared to ab initio valence-space in-medium similarity renormalization group (VS-IMSRG) calculations including contributions of two-body currents as well as to shell-model calculations. The two-body-current contributions significantly improve the agreement with experimental data, reducing the mean-square deviation from the experimental moments by a factor of 3 to 5, depending on the employed interaction. For all interactions, the largest contributions are obtained for the 52− (72−) isotopes 65Ni (55Ni), which is ascribed to the high angular momentum of the f orbitals. Our results demonstrate that the inclusion of two-body-current contributions to the magnetic moment in an isotopic chain of complex nuclei can be handled by the VS-IMSRG and can outperform phenomenological shell-model calculations using effective g-factors in the nickel region.

On the one hand, Ni3-xCoxB2O6 solid solutions are promising anode materials for lithium batteries, and on the other hand, they have antiferromagnetic properties. This study examines the lattice dynamics of Ni3-xCoxB2O6 solid solutions for x = 0, 1, 2, 3 by means of quantum chemistry and Raman spectroscopy. The vibrational spectra of the compound NiCo2B2O6 have been studied using the polarized Raman spectroscopy method. Good agreement was found between the theoretical and experimental results. As expected, the largest change in frequencies was observed in the modes where the vibrations of the metal ion had a large amplitude. The substitution of cobalt by nickel does not lead to the appearance of soft modes. This fact indicates that the structures of the solid solutions are stable.

In the present work, the electronic structure, elastic parameters, density of states (partial and total), optical properties, and charge density of ZrB5 (B = Se, Te) have been investigated by means of first principles calculations. The generalized gradient approximation has been used for modeling the exchange-correlation effects. It has been observed that the calculated lattice parameter values are in agreement with the values in the literature. The second-order elastic constants were calculated, and the other related quantities have also been estimated. The electronic band structures and the partial density of states corresponding to these band structures of ZrSe5 and ZrTe5 are examined, and it is understood that ZrTe5 and ZrSe5 are narrow band semiconductors or semimetals. Finally, the electron energy loss function (ELS) spectra and charge density of ZrB5 are calculated and interpreted. [ABSTRACT FROM AUTHOR]

The primary objective of this study is to investigate the influence of spin-orbit coupling and atom type on the electronic, optical, and thermoelectric properties of LuXNi2Sn2 (X = V, Nb, and Ta) double-half Heusler alloys. To achieve this, calculations were performed using the full potential linearized augmented plane wave method within the framework of density functional theory. Both full relativistic and scalar relativistic calculations were employed. The exchange-correlation interactions in this study were modeled using the PBEsol version of the generalized gradient approximation when calculating the structural ground state parameters. For the analysis of electronic, optical, and thermoelectric properties, the modified Becke–Johnson potential was employed. The modified Becke–Johnson potential was specifically chosen for its capability to improve the description of band gaps, particularly for systems with small band gaps, such as the LuXNi2Sn2 (X = V, Nb, and Ta) double-half Heusler materials examined in this study. This potential offers a more accurate representation of the electronic properties, enabling a more reliable analysis of the optical and thermoelectric characteristics of the materials under investigation. The examined LuXNi2Sn2 (X = V, Nb, and Ta) materials exhibit semiconductor behaviour, with band gaps smaller than 0.4 eV that can be controlled by varying the "X" atom. The charge carriers, specifically holes and electrons, exhibit light effective masses, indicating high mobility. Furthermore, these compounds exhibit low thermal expansion coefficients and satisfy the criteria for thermodynamic stability. In terms of optical properties, they display substantial absorption coefficients in the ultraviolet (UV) light region, high optical conductivity, and high reflectivity in the visible light region. Considering their favourable power factor and figure of merit characteristics, the LuXNi2Sn2 (X = V, Nb, and Ta) materials possess the potential to be promising candidates for thermoelectric applications. [ABSTRACT FROM AUTHOR]

To improve the understanding of the structure network of chalcogenide glass, we report an investigation of the structure and vibrational property of the Ge-S-Br system chalcogenide glass. The structural origin was interpreted by the result of ab initio calculation performed on the basic units such as ethane-like(ETH) structure(Ge2S6 and Ge2Br6),edge-sharing(ES) structure Ge2S2SnBr4-n (n=0,1,2,3,4) and isolated GeSnBr4-n tetrahedron (n=0,1,2,3,4), which represent the local structure of Ge-S-Br glassy system. In addition, We have compared the experimental spectra of GeS2, GeS3Br, GeSBr2 glasses and liquid GeBr4 to the calculated main vibrational modes of basic units by ab initio calculation. The calculated vibrational modes of the GeSnBr4-n cluster are assigned by group theory. Moreover, the symmetrical stretching modes related to the Ge-S and Ge-Br bond are in accordance with the vibrational coupling theory. The variation of calculated main vibrational modes of GeSmBrn clusters reveals the structure formations of Ge-S-Br glassy system with different S/Br ratios, which can be in agreement with vibrational spectra of Ge-S-Br glass. [ABSTRACT FROM AUTHOR]

The influence of size effects on the properties of a hexagonal boron nitride (h-BN) single layer containing CBVN, NBVN, and OBOBVN defects is studied by ab initio simulation. These defects are potentially capable of generating single photons in quantum optics and quantum information devices. Size effects here mean the dependence of the studied model properties on the simulated fragment size of a 2D structure under periodic boundary conditions. Physically, this means that the properties of a single layer depend on the distance between defects. This dependence allows us to judge how strongly the defects interact with each other and whether they interact at all. For technical applications, the characteristics of the band structure (band gap, spectrum, and density of electron states induced by the defect in the band gap) and the atomic structure of the defect (defect-formation energy, geometry in the equilibrium configuration), which form this band pattern, are important. In this work, these properties are studied using density functional theory with the basis of atom-like functions (SIESTA package) and plane waves (VASP package). The results obtained using both packages are consistent with each other. It is established that the defects can be considered noninteracting, when the distance between them is ten unit-cell parameters. [ABSTRACT FROM AUTHOR]

Context: The complexes formed as a result of the interactions between cyanophosphine (CP, H2PCN) and hypohalous acid molecules (HOX, X = F, Cl, Br, and I) were studied by employing ab initio computations conducted at the MP2/aug-cc-pVTZ level. Three types of complexes were acquired (I, II, and III) as a result of the (O∙∙∙P) pnicogen bond, the (N∙∙∙H) hydrogen bond, and the (N∙∙∙X) halogen bond interaction, respectively. The results of harmonic vibrational frequency calculations with no imaginary frequencies confirmed the structures as minima. In addition, given the interaction energy of the complexes, hydrogen bond complexes of structure II have the highest stability compared to other structures. In all studied complexes, the strength of the interactions depended on the electronegativity of the halogen atoms. The characteristics and nature of the whole three types of complexes were examined and evaluated with natural bond orbital (NBO), atom in molecules (AIM), molecular electrostatic potential (MEP) maps, non-covalent interaction (NCI) index, and electron density difference (EDD) analyses. Method: The optimization of all complexes and corresponding monomers was conducted through the ab initio method, employing the MP2 level along with the aug/cc-pVTZ basis set for all atoms, except for the iodine (I) atom, for which the aug-cc-pVTZ (PP) basis set was employed. Subsequent frequency calculations were executed to ascertain the minimum energy state of the complexes at the MP2 level and the aug/cc-pVTZ basis set, utilizing Gaussian09 software. The MEP maps of the monomers were generated using the analysis-surface suite (WFA-SAS) software package. To probe the orbital interactions within the studied complexes, NBO analysis was performed employing NBO software. The assessment of bond nature, topological features, and electron density values at critical points for the studied complexes was undertaken using AIMAll software. The NCI index was derived utilizing Multiwfn software, and its three-dimensional representation was rendered using VMD software. [ABSTRACT FROM AUTHOR]

Abstract Davemaoite, that is, CaSiO3 perovskite (CaPv), is the third most abundant phase in the lower mantle and exhibits a tetragonal‐cubic phase transition at high pressures and temperatures. The phase boundary in CaPv has recently been proposed to be close to the cold slab adiabat and cause mid‐mantle seismic wave speed anomalies (Thomson et al., 2019, https://doi.org/10.1038/s41586‐019‐1483‐x). This study utilized accurate deep‐learning‐based simulations and thermodynamic integration techniques to compute free energies at temperatures ranging from 300 to 3,000 K and pressures up to 130 GPa. Our results indicate that CaPv exhibits a single cubic phase throughout lower‐mantle conditions. This suggests that the phase diagram proposed by Thomson et al. requires revision, and mid‐mantle seismic anomalies are likely attributable to other mechanisms.

In this study, a novel 3,3′-bipyrazolo [3,4-b]pyridine-type structure was synthesized from 5-acetylamino-3-methyl-1-phenylpyrazole using the Vilsmeier-Haack reaction as a key step. The spectroscopic properties and structural elucidation of the compound were determined with the use of FT-IR, HRMS, 1H NMR, and 13C NMR. Likewise, the theoretical analysis of the IR and NMR spectra allowed peaks to be assigned and a solid correlation was demonstrated between the experimental and theoretical results. Finally, ab initio calculations based on the density functional theory method at the B3LYP/6-311G (d,p) level of theory were used to determine the conformational energy barrier, facilitating the identification of the most probable conformers of the synthesized compound. Overall, our findings contribute to the understanding of bipyrazolo [3,4-b]pyridine derivatives.

In this work, taking the Pr(III) ion as a suitable case study, the authors test the capacity of a series of Gaussian Type Orbitals (GTOs) basis sets to account for the atomic spectra of lanthanide ions. An extended relevance of this assessment can be found in modeling the luminescence of lanthanide-based materials. It was selected the Pr(III) case because it shows a rather rich collection of experimental data, emerging from the f2 and fd configurations. The energy barycenters of spectral multiplets can be equated analytically in terms of the so-called Slater-Condon parameters. By multi-configurational ab initio procedures, with basis sets from existing GTO repositories, the calculated f→f transitions are moderately higher than the experimental values, while the relative energies of fd states undergo both under- and over-estimation. The GTO shortcomings, that are impacting the accuracy, were debated, the critical perspective spreading the seeds of future development.

The effects of interfacial energy on precipitation behavior and physical properties of Cu–Ni–Si–(Co) alloys were investigated. The Cu–1.3Ni–0.3Si and Cu–1.3Ni–0.6Si–1.0Co alloys (in weight %) were prepared by combined cold-rolling and aging processes. The addition of Co promoted the formation of (Ni,Co)2Si by replacing Ni with Co in Ni2Si. Ab initio calculations demonstrated that the small addition of Co considerably reduced the interfacial energy between the Cu matrix and (Ni,Co)2Si, which effectively decreased the activation energy for precipitation. As a result, the precipitation of fine rod-shaped (Ni,Co)2Si was accelerated during the aging process and the number density of the precipitates increased up to 9.0 × 1010 cm−2. The nano-scale (Ni,Co)2Si precipitates with an average size of 13.5 nm strengthened the alloy properly through the Orowan mechanism without much loss of electrical conductivity. The maximum hardness and electrical conductivity were 220 Hv and 51 % International Annealed Copper Standard, respectively, for the Cu–1.3Ni–0.6Si–1.0Co alloy aged for 4 h at 420 °C.

We performed ab initio valence-space in-medium similarity renormalization group calculations based on chiral nucleon-nucleon and three-nucleon interactions to study the neutron-rich nuclei around N=28, where the experimental and theoretical evidence point to a rapid transition from spherical to rotational regimes. First, the rotational spectra of 40Mg, 42Si, and 44S are established theoretically, anchored by the calculated E2 transition strength. The results suggest that 40Mg and 42Si exhibit large deformations. After that, the erosion of the N=28 shell closure, especially the evolutions of shape deformation and the emergence of shape coexistence, are discussed in N=28 even-even isotones ranging from 40Mg to 48Ca. Finally, the shell evolution of N=28 in Mg and Si chains is discussed based on the experimental and predicted excitation energies of low-lying states. The results from our ab initio calculations align well with available experimental data, furnishing essential insights into the structure of neutron-rich nuclei, particularly deformations in the vicinity of 40Mg and 42Si.

We explore the transport properties of oligophenylene molecular junctions, where the center molecule containing 1, 2, or 3 phenyls is sand-wiched between two graphene nanoribbons (GNR) with different edge shapes. According to the obtained results of the first-principles calculations combined with non-equilibrium Green's function method, we find that the molecular length-dependent resistance of all examined oligophenylene molecular junctions follows well the exponential decay law with different slopes, and the exponential decay factor is sensitive to the edge shape of GNRs and the molecule-electrode connecting configuration. These observations indicate that the current through the oligophenylene molecular junction can be effectively tuned by changing the edge shape of GNRs, the molecular length, and the molecular contacting configuration. These findings provide theoretical insight into the design of molecular devices using GNRs as electrodes. [ABSTRACT FROM AUTHOR]

Our study on functional metal oxides for the past 45 years is reviewed. Conversion Electron Mössbauer Spectroscopy (CEMS) and the depth selective CEMS (DCEMS) using a gas-flowing detector are useful in characterizing the surface layer of oxide on steel and stainless steel. The thin oxide layer on stainless steel responds well as a pH sensor. 57Fe implanted SiO2 glass becomes a transparent and magnetic material. Semiconductor SnO2 films doped with dilute Fe and super dilute Fe are characterized by 57Fe and 57Mn ions implantation, respectively. The experimental results of dilute Fe doped SnO2 are supported by ab initio calculation of the configuration models. Inelastic nuclear resonance scattering gives a vibration DOS of double perovskite oxides, which can absorb CO2 rapidly at high temperatures. The new research will be developed on the base of the past studies. [ABSTRACT FROM AUTHOR]

A series of mixed orthovanadates with nominal composition Lu0.5R0.5VO4 (R = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) were synthesized by a solid-state reaction method in the three-stage annealing process. The single-phase powders with smaller Eu, Tb, Dy, Ho, Er, Tm, Yb were obtained after the second calcined stage at 1200 C for 5h, while for large Ce, Pr, Nd, Sm needed a third calcining. Rietveld refinement analysis of the crystal structure confirms a zircon-type structure (space group I41/amd). Furthermore, a linear dependence of the obtained lattice parameters on the ionic radius of the substituted lanthanide R was observed in the mixed Lu0.5R0.5VO4 series. The lattice parameters optimized by ab initio methods are slightly smaller than parameters obtained by Rietveld refinement, which can be explained by inaccuracies in the description of f-electrons using density functional theory (DFT). The transmission and diffuse reflectance spectra of mixed compounds Lu0.5R0.5VO4 are similar to such spectra obtained for corresponding orthovanadates RVO4. Both obtained spectra indicated significant differences in transmission/reflection intensities between samples annealed at 1200 °C and 1400 °C, but the band gap width remained unchanged, suggesting an improvement their crystallinity. Both experimental and theoretical results reveal a barely noticeable reduction in the band gap observed with a reduction of the ionic radius of the lanthanides. A thorough analysis of the electronic structure of the materials and diffuse reflectance spectra suggests that the position of the f-levels of lanthanides is the determining factor in the formation of valence and conduction bands. [ABSTRACT FROM AUTHOR]

Numerical studies on the effect of surface relaxation, namely, the equilibrium change in the interplanar distance, exerted on the values of the magnetic and energy characteristics of a Fe/Pt/Fe system have been performed. The contribution of spin-orbit coupling to the value of magnetic anisotropy energy is studied as a function of ferromagnetic film thickness. [ABSTRACT FROM AUTHOR]

Magnetic phase transitions in alloys are highly influenced by the sample preparation techniques. In the present research, electronic and magnetic properties of Fe48Cr3Rh49 alloys with varying cooling rates were studied, both experimentally and theoretically. The degree of crystalline ordering was found to depend on the cooling rate employed after annealing the alloy. Modeling of alloy structures with different degrees of crystalline ordering was carried out via strategic selection of substitution positions and distances between chromium atoms. Theoretical calculations revealed significant changes in magnetic and electronic properties of the alloy with different substitutions. A comprehensive analysis of the calculated and experimental data established correlations between structural characteristics and parameters governing the magnetic phase transition. In this study, we also developed a method for evaluating the magnetic properties of the alloys obtained under different heat treatments. The proposed approach integrates atom substitution and heat treatment parameters, offering precise control over alloy manufacturing to effectively tune their essential magnetic properties. [ABSTRACT FROM AUTHOR]

New magic numbers have been discovered in the neutron-rich region of the nuclear chart. However, there has been a lack of research on proton-rich nuclei. 22O, the mirror nucleus of 22Si, is a double-magic nucleus bearing a high E(21+). Whether 22Si exhibits double-magic characters is an intriguing topic. To investigate this matter, we utilized ab initio valence space in-medium similarity renormalization group for 22Si/22O, and their nearby nuclei. Our ab initio calculations provide good descriptions for the double magicity of 22O, as well as the shell evolution of N=14 and Z=14 through E(21+). The computed E(21+) indicate that the closure of Z=14 sub-shell in proton-rich nuclei is weaker than the N=14 sub-shell closure in their mirror nuclei. Particularly, the calculated E(21+) of 22Si is 800 keV lower than the one of 22O. To further explore the magicity of 22Si, the mirror energy difference (MED) of 26Si/26Mg, 24Si/24Ne, as well as 22Si/22O are calculated. The results demonstrate that the calculated MEDs agree well with available experimental data, and the E(21+) values of 22,24,26Si are all lower than their respective mirror nuclei due to the Thomas-Ehrman shift with large s1/2 occupation. Moreover, our calculation provides that the many-body configurations of the low-lying state of 22Si/22O are nearly identical despite the fact that the states bearing large MED. In conclusion, our ab initio results suggest that 22Si is a double magic nucleus, similar to its mirror nucleus 22O, albeit with a lower E(21+).

The paper presents a study on the vibrational spectra of four different compounds, namely, methyl acrylate (MA), methyl methacrylate (MMA), methyl trans crotonate (MTC), and methyl-3-methoxy-2-propenoate (MMP), in their electronic ground state using the Hartree-Fock and Density Functional Theory calculations with extended basis sets and polarization functions. The study compares the outcomes of the possible conformers in terms of their frequency, form, and intensity of vibrations, as well as the potential energy distribution across the symmetry coordinates in the ground state. Moreover, the study examines the relationship between bond length and bond order. [ABSTRACT FROM AUTHOR]

In the presented article a relationship between the structure of defects in CdSexTe1 – x (x = 0.4) and its kinetic properties is established. For the first time, a method for determining the energy spectrum, wave function, and self-consistent crystal potential in CdSe0.4Te0.6 at a predetermined temperature is proposed. Within the framework of the supercell method, the structure of defects is studied and the temperature dependences of the ionization energies of various types of defects are determined. The proposed method also makes it possible to determine the temperature dependences of the optical and acoustic deformation potentials, as well as the temperature dependence of electron scattering parameters on different types of crystal defects. Within the framework of the short-range scattering models, the dependences of the electron mobility and electron's Hall factor vs temperature are established. [ABSTRACT FROM AUTHOR]

The study provides novel insights into the crystal–chemical and optical characteristics of frankamenite. Frankamenite belongs to a special group (canasite group) of the complex alkaline Ca-(K)-(Na) silicates, and it was found in charoitites from the only known location, Murun Massif, Eastern Siberia, Russia. The crystal–chemical, vibrational, and optical properties of frankamenite were investigated by combining electron probe microanalysis (EPMA), single-crystal X-ray diffraction (SCXRD), infrared (IR) absorption, Raman, UV-Visible absorption, and electron spin resonance (ESR) spectroscopy. The behavior of the peaks in the IR spectra was also studied using ab initio calculations. Detailed characteristics of the internal composition and structure of the mineral species were described, and vibrational and optical properties based on these peculiarities were interpreted. The thermally stimulated reorientation of the H2O molecules and OH− groups was studied by thermo-Raman spectroscopy. Octahedral cationic positions can be readily doped with transition metal and lanthanide ions that provide a promising opportunity to adjust the Ce3+ luminescence. Hence, frankamenite is a potential material for ion exchange, novel phosphors, and luminophores. [ABSTRACT FROM AUTHOR]

Using the ab initio methods of quantum chemistry, a detailed theoretical investigation of oligomeric products, that reproduce some features of the structure for typical fragments of lignin macromolecules have been carried out. The structuring of individual sections has done on the basis of trans-coniferyl alcohol as a prototype with its subsequent dimerization for three pairs of isomeric compounds with different types of linkages. Their ranking according to the level of relative thermodynamic stability showed, that the forms (α-O-4), (β-β) and (5-5) are the most stable, while the structures (β-O-4), (β-5) and (4-O-5) turned out to be the less stable ones. When substantiating of the spectral characteristics for these systems with the calculation of vibrational frequencies in the harmonic approximation, considerable attention was paid to the intramolecular hydrogen bonding effects, which occur with some participation of spatially complicated hydroxyl groups of the alcohol or phenolic type, as well as the analysis of the rigid chain of pinoresinol system, which contains a bicyclic cage fragment. The results of calculations are in good agreement with the IR spectral data obtained experimentally, and may be of fundamental importance from the point of view about searching of potential precursor compounds for further structuring of this irregular biopolymer. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerator has extensive applicability because of its capability of harvesting mechanical energy and flexible working modes. To research the optimum pressure and improve the recovered energy of the sliding-mode triboelectric nanogenerator, a contact model of the Al/PTFE tribo-pair is studied by ab initio calculation and finite element simulation. The F-atom of PTFE is proved to be the electron accepter and the charges transferred can be predicted by Bader charge analysis. The mathematical relation between interfacial distance, charges transferred and contact pressure can be fitted. By Gauss’s law, the electric field is simulated and the regeneration energy of the sliding-mode triboelectric nanogenerator can be evaluated by the total electric energy and friction loss. Finally, an optimum pressure can be set to the upper or lower limit of working pressure corresponding to larger recovered energy. And less friction coefficient and larger contact area are also effective methods for recovering energy.

In the presented article the method of determining the energy spectrum, the wave function of the charge carrier and the crystal potential in CdTe at an arbitrarily given temperature is considered. Using this approach within the framework of the supercell method the temperature dependences of the ionization energies of various types of defects caused by the introduction of chlorine and copper impurities in cadmium telluride are calculated. Also the offered method allows to define the temperature dependence of the optical and acoustic deformation potentials and as well as the dependence on the temperature the charge carrier’s scattering parameters on ionized impurities, polar optical, piezooptic and piezoacoustic phonons. Within the framework of short-range scattering models the temperature dependences of the charge carrier’s mobility and Hall factor are considered.

The results of studying the effect on the crystal structure and magnetic properties of compounds based on NiMnSb when Ni cations are replaced by Fe and Co cations are presented. The solid solution Ni1–xMxMnSb (M = Fe, Co) systems were synthesized by the method of solid-phase reactions. With the help of X-ray diffraction analysis, the presence of a concentration structural transition was established. Using the ponderomotive method, it was found that the temperatures of the “magnetic order – magnetic disorder” phase transformation decrease as nickel is replaced by iron and cobalt. The field dependences of the specific magnetization demonstrate the typical behavior of a magnetically soft ferromagnet. The results of an experiment on the study of the crystal and magnetic structure of solid solutions of the Ni0.90M0.10MnSb (M = Fe, Co) systems using thermal neutron diffraction in the temperature range of ~(3–300) K are presented. It is found that the studied compositions exhibit ferromagnetic ordering along the c axis. On the spectra of Ni0.90Co0.10MnSb solid solutions in the region of 2Θ = 28.6° the appearance of a reflection indicating the formation of antiferromagnetic ordering is observed. Within the framework of the density functional theory, an ab initio calculation of the magnetic moments for Ni1-xMxMnSb (M = Fe, Co; x = 0; 0.125; 0.250) was carried out. The results of theoretical calculations predict the existence of magnetic moments for Fe and Co ions, and they are antiferromagnetically coupled to the spins of Mn and Ni ions.

We investigated the structure, elastic, and thermodynamic properties of Hf-Ta-C-N solid solutions using high-throughput density functional theory calculations. The results of the elastic and mechanical properties indicate that increasing the nitrogen content increases the ductility of solid solutions; it also increases the elastic moduli of solid solutions in a specific range of nitrogen contents. The results indicate that the ternary and quaternary solid solutions of the Hf-Ta-C-N system have excellent formability, elastic, and thermal properties. In addition, thermodynamic analyses were performed to obtain temperature-dependent stable phase diagrams of the Hf-Ta-C-N quaternary system. This investigation was performed to determine the suitability of Hf-Ta-C-N quaternary solid solutions in high temperature condition, which was veiled in previous studies. In total, 51 related phases were studied, including 16 solid solutions and four elemental phases (Hf, Ta, C, and N2(g)). Our results indicate that the nitrogen-rich solid solutions can appear even at room temperature. The solid solutions covered a large area of the Hf-Ta-C-N phase spaces, regardless of temperature. As the temperature increases, the stable phase shifts from Ta and N to the Hf and C rich phases.

Autonomous material search systems that combine ab initio calculations and Bayesian optimization are very promising for exploring huge material spaces. Setting up an appropriate material search space is necessary for efficient autonomous material search. However, performing the autonomous search within the material space set up using the prepared descriptors is not sufficient to obtain an efficient search, which can be achieved by prioritizing specific descriptors and properties. Here, a material search system that can autonomously search the huge material space while performing multi-objective optimization that considers similarities among elements and emphasizes specific descriptors is proposed. This system has been used for a material exploration of Heusler alloys. The system has successfully proposed several candidate materials with half-metallic properties. The proposed system is very versatile and can be applied to various properties and material systems.

The calculation of the density of states of various thicknesses of the 2D-layers of the intermetallic compound RbAu has been carried out. 2D-layers of intermetallic compound RbAu are simulated by supercells RbAu (111) 2×2×2. For a monolayer 2D-layer of an intermetallic compound RbAu the presence of a bandgap with a width of 2,70 eV has been established. An increase in the thickness of the 2D-layers of the intermetallic compound RbAu to three monolayers showed a decrease in the bandgap to 0,80 eV. A further increase in the thickness of the 2D-layers of the intermetallic compound RbAu leads to the disappearance of the band gap, which indicates a semiconductor-metal transition for the 2D-layer of the intermetallic compound RbAu with a thickness of four monolayers. The valence band of the 2D-layer of the intermetallic compound RbAu is formed mainly by Au 5d electrons, with an insignificant contribution from Au 6s and Au 6p electrons. The conduction band of RbAu is formed mainly by Au 6p electrons with an insignificant contribution of electrons Rb 5s.

Abstract Over the past few decades, hydrous minerals were thought to be absent in the lower mantle, due to their instability at high-pressure conditions. Recently, however, hydrous phases including phase H (MgSiO $$_4$$ 4 H $$_2$$ 2 ), pyrite-type FeOOH, and $$\delta$$ δ -AlOOH have been discovered to be thermodynamically stable at lower mantle pressures. Investigations using ab initio calculations methods play a key role in identifying these novel phases and determining their geophysical properties (i.e., compressibility, elasticity, and sound velocities). These calculations suggest that the hydrous minerals which are stable at lower mantle pressure conditions (i.e., phase H, FeOOH, and AlOOH), have symmetric hydrogen bonds at these pressures. This indicates that hydrogen bond strength is closely connected to the stability and physical properties of hydrous minerals at extreme pressures. In this review, we summarize the theoretical and experimental studies of hydrous minerals stable at the high-pressure conditions of the Earth’s lower mantle in light of the role of hydrogen bonding.

Chalcopyrites are ternary semiconductor compounds with successful applications in photovoltaics. Certain chalcopyrites are well researched, yet others remain understudied despite showing promise. In this study, we use ab initio methods to study CuGaS2, AgGaS2, and CuGaSe2 chalcopyrites with a focus on their less studied solid solutions. We use density functional theory (DFT) to study the effects that atomic configurations have on the properties of a solid solution and we calculate the optical absorption spectra using a many-body perturbation theory. Our theoretical simulations predict that excess of In and Se in the solid solutions leads to narrowing of the band gap and to the broadening of the absorption spectra. Obtained results show promise for possible photovoltaic applications, as well as developed methodology can be used for further study of other promising chalcopyritic compounds. [ABSTRACT FROM AUTHOR]

Interactions in a multicomponent Ni-Cr-Mo-Al-Re model alloy were determined by ab initio calculations in order to investigate the Re doping effect on Haynes 282 alloys. Simulation results provided an understanding of short-range interactions in the alloy and successfully predicted the formation of a Cr and Re-rich phase. The Haynes 282 + 3 wt% Re alloy was manufactured using the additive manufacturing direct metal laser sintering (DMLS) technique, in which the presence of the (Cr17Re6)C6 carbide was confirmed by an XRD study. The results provide useful information about the interactions between Ni, Cr, Mo, Al, and Re as a function of temperature. The designed five-element model can lead to a better understanding of phenomena that occur during the manufacture or heat treatment of modern, complex, multicomponent Ni-based superalloys. [ABSTRACT FROM AUTHOR]

Recently, phonons with chirality (chiral phonons) have attracted significant attention. Chiral phonons exhibit angular and pseudoangular momenta. In circularly polarized Raman spectroscopy, the peak split of the Γ3 mode is detectable along the principal axis of the chiral crystal in the backscattering configuration. In addition, peak splitting occurs when the pseudoangular momenta of the incident and scattered circularly polarized light are reversed. Until now, chiral phonons in binary crystals have been observed, whereas those in unary crystals have not been observed. Here, we observe chiral phonons in a chiral unary crystal Te. The pseudoangular momentum of the phonon is obtained in Te by an ab initio calculation. From this calculation, we verified the conservation law of pseudoangular momentum in Raman scattering. From this conservation law, we determined the handedness of the chiral crystals. We also evaluated the true chirality of the phonons using a measure with symmetry similar to that of an electric toroidal monopole. [ABSTRACT FROM AUTHOR]

Using the calculation and experimental techniques, we studied the effect of cold rolling to degrees of 85 and 90% on the structural and textural condition, microdurometric and elastic properties of the following quenched biocompatible β-titanium alloys (in at %): Ti–26% Nb–3% Zr, Ti–26% Nb–5% Zr, Ti–26% Nb–6% Zr, Ti–26% Nb–3% Zr–1% Sn, Ti–26% Nb–3% Zr–1% Sn–0.7% Ta. It is shown that an increase in the degree of deformation at cold rolling promotes the formation of a more pronounced two-component texture {001}ββ, {112}ββ, a growth in the microhardness, and a decrease in the values of the elastic modulus in the plane of rolling. It is established that there is good agreement between the calculation and experimental values of the elastic modulus of these alloys in the quenched and cold-rolled state. The effect of alloying and anisotropic state of the alloys (via the molybdenum equivalent and the Zener anisotropy index, respectively) on the levels of their microhardness, contact elastic modulus E, including the difference in E in different sections of cold-rolled sheet,—is considered. Those compositions of alloys and the modes of deformation are determined that allow one to obtain the lowest values of their own elastic moduli. [ABSTRACT FROM AUTHOR]

Oxygen transport through environmental barrier coating (EBC) to form thermally grown oxide (TGO) on the bond coat greatly affects the service life of the EBC when it is subjected to severe environments. In this work, the oxygen diffusion behaviours through barium–strontium aluminosilicates (BSAS), a typical EBC material, were investigated via ab initio molecular dynamic calculations. The results of these calculations are then verified via isotope exchange experiments. It was found that the interstitial oxygen can stably exist and diffuse through the BSAS. Three interlaced diffusion channels in the structure of BSAS were found to form a complete three-dimensional diffusion network. It was also found that the bond length of Si–Al–O can serve as a measure of the diffusion of interstitial molecular oxygen in BSAS. The oxygen permeability of BSAS can be decreased by adjusting the proportions of alkaline earth elements present in the structure, which modifies the bond lengths within the structure. The solution of alkaline earth elements increases the local migration energy barrier, leading to an increase in the overall migration energy barrier. [Display omitted] [ABSTRACT FROM AUTHOR]