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Boron neutron capture therapy (BNCT) has been extant for decades and continues to be practiced in many centers around the globe. Most of the active clinical trials utilize boronophenylalanine as the drug containing boron atoms. The important aspect that has been added to the BNCT practice is the use of an F-18 radiolabeled analog for ascertaining targeting and monitoring follow-up studies. The recent widespread application of therapeutic radiopharmaceuticals, especially peptides (somatostatin analogs), prostate-specific antigen-binding ligands, or immunomolecules, offers the ambit for invention of new tumor-specific BNCT agents, especially for BNCT-susceptible tumors, that is, locoregional cancers such as head and neck cancer. Such BNCT agents, when radiolabeled, can enable simultaneous imaging and/or therapeutic applications (depending on the radionuclide used) through multimodal approaches. Development of boron-rich moieties such as sodium borocaptate and neutral carboranes combined with tumor-targeting moieties can lead to a new horizon in BNCT. The review covers various aspects of drug design, tumor targeting, and possible future radiopharmaceutical development for multimodal theranostic application in humans.

Four new double perovskites, SrLaMReO(6) (M = Mg, Mn, Co, Ni) in which Re(5+) (5d(2)) is present, were prepared via conventional solid state reactions and characterized by X-ray and neutron powder diffraction, XANES, SQUID magnetometry, and muon spin relaxation (μSR). Synchrotron X-ray and neutron diffraction experiments confirmed that all compounds crystallize in the monoclinic P2(1)/n structure type, which consists of alternately corner-shared octahedra of MO(6) and ReO(6). Rietveld refinement results indicated anti-site mixing of less than 7% on the M/Re sites. Bond valence sum calculations (BVS) suggest all M and Re ions are 2+ and 5+, respectively, and for the Mn-containing phase this is also supported by XANES measurements. All of the materials are paramagnetic at room-temperature and their Curie-Weiss temperatures are positive (except for Mg) indicating net ferromagnetic interactions. No evidence for long-range magnetic order is evident in the dc magnetic susceptibility and μSR measurements for SrLaMgReO(6) to 2 K. The Mn-phase shows long-range order at T(C) = 190 K and neutron diffraction revealed a ferromagnetic structure with a refined net moment of ∼3.7μ(B). Both Co- and Ni-containing phases exhibit spin glass behavior at T(G) = 23 and 30 K, respectively, which is supported by neutron diffraction and a.c. susceptibility data. The structure and physical properties of these four new rhenium based ordered double perovskites are compared to the closely related "pillared perovskites", La(5)Re(3)MO(16), the isoelectronic Os(6+) (5d(2)) double perovskite Sr(2)CoOsO(6), and the Re(6+) (5d(1)) double perovskites, Sr(2)MReO(6), (M = Mg, Ca, Mn, Co, Ni).

Single-crystal diffuse scattering data have been collected at room temperature on synthetic titanite using both neutrons and high-energy x-rays. A simple ball-and-springs model reproduces the observed diffuse scattering well, confirming its origin to be primarily due to thermal motion of the atoms. Ab initio phonons are calculated using density-functional perturbation theory and are shown to reproduce the experimental diffuse scattering. The observed diffuse x-ray and neutron scattering patterns are consistent with a summation of mode frequencies and displacement eigenvectors associated with the entire phonon spectrum, rather than with a simple, short-range static displacement. A band gap is observed between 600 and 700 cm(-1) with only two modes crossing this region, both associated with antiferroelectric Ti-O motion along a. One of these modes (of Bu symmetry), displays a large LO-TO mode-splitting (562-701.4 cm(-1)) and has a dominant component coming from Ti-O bond-stretching and, thus, the mode-splitting is related to the polarizability of the Ti-O bonds along the chain direction. Similar mode-splitting is observed in piezo- and ferroelectric materials. The calculated phonon dispersion model may be of use to others in future to understand the phase transition at higher temperatures, as well as in the interpretation of measured phonon dispersion curves.

The compound La(3)Re(2)O(10) has been synthesized by solid-state reaction and characterized by powder neutron diffraction, SQUID magnetometry, and heat capacity measurements. Its structure consists of isolated [Re(2)O(10)](9-) dimer units of two edge-shared ReO(6) octahedra, separated by La(3+) within the lattice. The Re-Re distance within the dimer units is 2.488 A, which is indicative of metal-metal bonding with a bond order of 1.5. The average oxidation state of the Re atom is +5.5, leaving one unpaired electron per dimer unit (S = 1/2). Although the closest interdimer distance is 5.561 A, the magnetic susceptibility data and heat capacity measurements indicate this compound exhibits both short- and long-range magnetic order at surprisingly high temperatures. The zero field cooled (ZFC) magnetic susceptibility data show two broad features at 55 and 105 K, indicating short-range order, and a sharper cusp at 18 K, which signifies long-range antiferromagnetic order. The heat capacity of La(3)Re(2)O(10) shows a lambda-type anomaly at 18 K, which is characteristic of long-range magnetic order. DFT calculations determined that the unpaired electron resides in a pi-bonding orbital and that the unpaired electron density is widely delocalized over the atoms within the dimer, with high values at the bridging oxygens. Extended Hückel spin dimer calculations suggest possible interaction pathways between these dimer units within the crystal lattice. Results from the calculations and fits to the susceptibility data indicate that the short-range magnetic ordering may consist of 1-D antiferromagnetic linear chains of coupled S = 1/2 dimers. The magnetic structure of the antiferromagnetic ground state could not be determined by unpolarized neutron powder diffraction.

The presence of defects at the interface between the perovskite film and the carrier transport layer poses significant challenges to the performance and stability of perovskite solar cells (PSCs). Addressing this issue, we introduce a dual host-guest (DHG) complexation strategy to modulate both the bulk and interfacial properties of FAPbI3-rich PSCs. Through NMR spectroscopy, a synergistic effect of the dual treatment is observed. Additionally, electro-optical characterizations demonstrate that the DHG strategy not only passivates defects but also enhances carrier extraction and transport. Remarkably, employing the DHG strategy yields PSCs with power conversion efficiencies (PCE) of 25.89% (certified at 25.53%). Furthermore, these DHG-modified PSCs exhibit enhanced operational stability, retaining over 96.6% of their initial PCE of 25.55% after 1050 hours of continuous operation under one-sun illumination, which was the highest initial value in the recently reported articles. This work establishes a promising pathway for stabilizing high-efficiency perovskite photovoltaics through supramolecular engineering, marking a significant advancement in the field. The defects at the perovskite/carrier transport layer interface pose significant challenges to the performance of perovskite solar cells. Here, the authors introduce a dual host-guest complexation strategy with Cs-crown-ether and ammonium salt, achieving a high PCE of 25.9% with superior stability. [ABSTRACT FROM AUTHOR]

An examination of the tilt modes and other low-frequency modes is made for an isolated, untilted perovskite layer, which maps very simply to the ABX4 perovskites. A sheet of pure tilts exists at the Brillouin Zone boundary at {xi, (1/2), zeta}. An instability is also found at all wavevectors which can be described as continuously varying from pure tilts to pure layer displacements as a function of the wavevector. Analysis is extended by considering the stacking of layers in the I-centered A2BX4-layer perovskites. The effect of freezing in the commensurate tilt required to generate the Cmca tilt system, pertinent to the modulated phases of propylammonium salts, is examined. The zero-frequency modes are restricted to two planes in the Brillouin Zone. All of the observed wavevectors associated with modulated phases, and the commensurately tilted propylammonium tetrachlorocadmate, are consistent with this calculation. The effect of full three-dimensional connectivity is briefly reviewed for the true ABX3 perovskites. While pure tilt incommensurates appear to be hypothetically possible, they do not appear to have been observed to date.

The heavy fermion system exhibits properties that range from an incommensurate antiferromagnet for small to an exotic superconductor on the Ir-rich end of the phase diagram. At intermediate where antiferromagnetism coexists with superconductivity, two types of magnetic order are observed: the incommensurate one of and a new, commensurate antiferromagnetism that orders separately. The coexistence of -electron superconductivity with two distinct -electron magnetic orders is unique among unconventional superconductors, adding a new variety to the usual coexistence found in magnetic superconductors.

The transformation of ammonium cyanate into urea, first studied over 170 years ago by Wöhler and Liebig, has an important place in the history of chemistry. To understand the nature of this solid state reaction, knowledge of the crystal structure of ammonium cyanate is a prerequisite. Employing neutron powder diffraction, we demonstrate conclusively that, in the structure of ammonium cyanate, the NH(4)(+) cation forms N-H...N hydrogen bonds to four cyanate N atoms at alternate corners of a distorted cube, rather than our previously proposed alternative arrangement with N-H...O hydrogen bonds to cyanate O atoms at the other four corners.

The crystal structure of chlorofluoromethane, CH(2)ClF, has been determined at 100 and 30 K using indexing, packing considerations and Rietveld refinement of neutron powder profiles. There is only one phase, in monoclinic space group P2(1) and with two molecules in the unit cell occupying general positions. The structure has close packing in several directions and there are weak hydrogen bonds forming zigzag chains.

Halide perovskites show great optoelectronic performance, but their favorable properties are paired with unusually strong anharmonicity. It was proposed that this combination derives from the ns2 electron configuration of octahedral cations and associated pseudo-Jahn–Teller effect. We show that such cations are not a prerequisite for the strong anharmonicity and low-energy lattice dynamics encountered in these materials. We combine X-ray diffraction, infrared and Raman spectroscopies, and molecular dynamics to contrast the lattice dynamics of CsSrBr3 with those of CsPbBr3, two compounds that are structurally similar but with the former lacking ns2 cations with the propensity to form electron lone pairs. We exploit low-frequency diffusive Raman scattering, nominally symmetry-forbidden in the cubic phase, as a fingerprint of anharmonicity and reveal that low-frequency tilting occurs irrespective of octahedral cation electron configuration. This highlights the role of structure in perovskite lattice dynamics, providing design rules for the emerging class of soft perovskite semiconductors. By comparing CsSrBr3 and CsPbBr3 with close structural similarity but the latter lacking lone-pair electrons on the octahedral metal, the authors reveal the similar vibrational anharmonicities in the two perovskites, which disentangles the electronic properties and vibrational anharmonicities. [ABSTRACT FROM AUTHOR]

The atomic scale solid–liquid interfacial process dominates the macro‐dissolution of silica, yet its direct experimental observation is challenging. Here we employed the reactive molecular dynamics to model this process in alkaline condition. An elevated temperature strategy under canonical ensemble (NVT) was applied to accelerate the process for sufficient sampling at temporal domain. A stepwise transformation from fully linked SiO4 network (Q3 and Q4) to reduced linkage and eventually aqueous species (Q0) was revealed. The simulated dissolution rate agrees well with the value predicted by empirical model. By tracing hydrogen atoms, we found that the dehydroxylated silica surfaces in alkaline electrolyte solutions underwent a transition from Si–O–Si bond cleavage‐dominated (mainly reacted with OH−) to hydroxylation‐dominated surface reactions. The free‐energy reconstruction of well‐tempered metadynamics reveals that 1500 K accelerates dissolution without altering the reaction pathways. These findings offer novel insights into the evolution of atomic‐scale surface configurations during the dissolution kinetics of silica. [ABSTRACT FROM AUTHOR]

Sm0.2Ce0.8O1.9‐ 30% Na2CO3 (Sm doped ceria (SDC)‐30N) nano‐composite electrolytes were densified in a single step via cold sintering process (CSP). At 200°C and 450 MPa of uniaxial pressure, samples up to 97% of their theoretical density could be obtained. The effect of processing parameters, such as temperature, uniaxial pressure, processing duration, and moisture content, on the densification of the nano‐composite electrolytes was investigated. The thermal, microstructural, and electrical properties of nano‐composites were investigated by differential scanning calorimetry, X‐ray diffractometer, scanning electron microscope, and EIS analysis. SDC crystallite sizes were found to be around 25 nm, barely coarsened after CSP by which the true nano nature of the nano‐composite could be preserved. Because, by conventional processing high density values could not be attained and high processing temperatures in excess of 600°C had to be used, promoting particle coarsening. The highest total electrical conductivity was found to be 2.2 × 10−2 S cm−1 at 600°C, with an activation energy of 0.83 eV for SDC‐30N nano‐composites. The present investigation revealed that the implementation of cold sintering technique resulted in significant enhancements in the densification of nano‐composite electrolytes, thereby rendering them suitable for efficient utilization in SOFC applications, as compared to the conventional production methods. [ABSTRACT FROM AUTHOR]

Boron neutron capture therapy (BNCT) is one of the most promising treatments among neutron capture therapies due to its long‐term clinical application and unequivocally obtained success during clinical trials. Boron drug and neutron play an equivalent crucial role in BNCT. Nevertheless, current clinically used l‐boronophenylalanine (BPA) and sodium borocaptate (BSH) suffer from large uptake dose and low blood to tumor selectivity, and that initiated overwhelm screening of next generation of BNCT agents. Various boron agents, such as small molecules and macro/nano‐vehicles, have been explored with better success. In this featured article, different types of agents are rationally analyzed and compared, and the feasible targets are shared to present a perspective view for the future of BNCT in cancer treatment. This review aims at summarizing the current knowledge of a variety of boron compounds, reported recently, for the application of BCNT. [ABSTRACT FROM AUTHOR]

The Pliensbachian–Toarcian transition was characterised by a drastic turnover from a cool climate to a period of rapid global warming. While the warming associated with the Early Toarcian Oceanic Anoxic Event is rather well-studied, the cause, intensity and extent of the preceding cooling in the late Pliensbachian are still discussed. Occurrences of glendonite play an important role in this debate, since glendonite is a pseudomorph after the cryophilic carbonate mineral ikaite. This study describes the first glendonite-bearing carbonate concretions from South Germany (Buttenheim clay pit, northern Franconian Alb), which represent the southernmost glendonite occurrence in the late Pliensbachian documented so far. Based on petrographical and sedimentological investigations as well as stable isotope analyses it is concluded that a low temperature was the main factor for ikaite formation in the studied section, suggesting that the late Pliensbachian cooling had a more far-reaching impact on the temperature of the European epicontinental sea than previously assumed. To explain the low temperatures required for ikaite precipitation, a model for the sea-ice driven formation of cold bottom-water masses on the continental shelf is proposed. The occurrence of several layers containing reworked hiatus concretions in the studied outcrop is interpreted as the result of recurrent sea-level falls caused by multiple glacial pulses characterising the overall cool climate in the late Pliensbachian. [ABSTRACT FROM AUTHOR]

Recent research has demonstrated that the CuFeTe2 compound has interesting physical properties. However, less research effort has been afforded to the study of the stable non-stoichiometric Cu1.1Fe1.2Te2 structure and electronic properties. In this paper, we report the synthesis and electronic properties of the non-stoichiometric (Cu, Fe) co-doped CuFeTe2 (Cu1.1Fe1.2Te2) with a stable single phase. The temperature-dependent resistance and magnetic susceptibility measurements showed an obvious phase transition from a semiconductor to metal when the temperature reached 360 K, revealing a spin-density-wave (SDW)-like state existing in the as-grown Cu1.1Fe1.2Te2, which has a higher SDW transition temperature than that of CuFeTe2. Interestingly, a spectral weight evolution of the angle-resolved photoemission spectroscopy in the study of the electronic structure of Cu1.1Fe1.2Te2 is observed at the same temperature of 360 K. Our work provides a scheme for exploration of novel physical phenomena related to SDW in two-dimensional materials. [ABSTRACT FROM AUTHOR]

Globally, rejuvenation of soil health is a major concern due to the continuous loss of soil fertility and productivity. Soil degradation decreases crop yields and threatens global food security. Improper use of chemical fertilizers coupled with intensive cultivation further reduces both soil health and crop yields. Plants require several nutrients in varying ratios that are essential for the plant to complete a healthy growth and development cycle. Soil, water, and air are the sources of these essential macro- and micro-nutrients needed to complete plant vegetative and reproductive cycles. Among the essential macro-nutrients, nitrogen (N) plays a significant in non-legume species and without sufficient plant access to N lower yields result. While silicon (Si) is the 2nd most abundant element in the Earth's crust and is the backbone of soil silicate minerals, it is an essential micro-nutrient for some plants. Silicon is just beginning to be recognized as an important micronutrient to some plant species and, while it is quite abundant, Si is often not readily available for plant uptake. The manufacturing cost of synthetic silica-based fertilizers is high, while absorption of silica is quite slow in soil for many plants. Rhizosphere biological weathering processes includes microbial solubilization processes that increase the dissolution of minerals and increases Si availability for plant uptake. Therefore, an important strategy to improve plant silicon uptake could be field application of Si-solubilizing bacteria. In this review, we evaluate the role of Si in seed germination, growth, and morphological development and crop yield under various biotic and abiotic stresses, different pools and fluxes of silicon (Si) in soil, and the bacterial genera of the silicon solubilizing microorganisms. We also elaborate on the detailed mechanisms of Si-solubilizing/mobilizing bacteria involved in silicate dissolution and uptake by a plant in soil. Last, we discuss the potential of silicon and silicon solubilizing/mobilizing to achieve environmentally friendly and sustainable crop production. [ABSTRACT FROM AUTHOR]

The exceptional optoelectronic properties of metal halide perovskites (MHPs) are presumed to arise, at least in part, from the peculiar interplay between the inorganic metal-halide sublattice and the atomic or molecular cations enclosed in the cage voids. The latter can exhibit a roto-translative dynamics, which is shown here to be at the origin of the structural behavior of MHPs as a function of temperature, pressure and composition. The application of high hydrostatic pressure allows for unraveling the nature of the interaction between both sublattices, characterized by the simultaneous action of hydrogen bonding and steric hindrance. In particular, we find that under the conditions of unleashed cation dynamics, the key factor that determines the structural stability of MHPs is the repulsive steric interaction rather than hydrogen bonding. Taking as example the results from pressure and temperature-dependent photoluminescence and Raman experiments on MAPbBr 3 but also considering the pertinent MHP literature, we provide a general picture about the relationship between the crystal structure and the presence or absence of cationic dynamic disorder. The reason for the structural sequences observed in MHPs with increasing temperature, pressure, A-site cation size or decreasing halide ionic radius is found principally in the strengthening of the dynamic steric interaction with the increase of the dynamic disorder. In this way, we have deepened our fundamental understanding of MHPs; knowledge that could be coined to improve performance in future optoelectronic devices based on this promising class of semiconductors. [ABSTRACT FROM AUTHOR]

The synthesis of monoclinic (γ) tungsten oxide (WO3) nanorods via facile Microwave-assisted hydrothermal route is reported in the present work. The structural characterization of the as-synthesized material by using X-ray diffraction and Fourier-transform infrared spectroscopy confirms the formation of crystalline WO3 phase. The morphology and microstructural study along with elemental composition of the material as obtained by scanning electron microscopy and transmission electron microscopy, respectively, reveals the generation of one-dimensional WO3 nanorods. The nanorods show substantial absorbance in the ultraviolet (UV) region with the bandgap and refractive index of 2.7 eV and 2.48, respectively. Here, the low value of bandgap without adding any catalyst or co-catalyst is attributed to the microwave treatment. The electrochemical properties of WO3 are studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The nanorods show high current density at different potentials and diffusion-controlled behavior as exhibited by Warburg impedance. The anodic as well as cathodic peak current values are seen to be increased after the deposition of the thin film of FTO substrate indicating the better diffusion of ions in the electrolyte. The capacitive and diffusive contribution of the thin film is investigated at various scan rates using Dunn's model which shows that the diffusive contribution of the thin film is 120 times more than the capacitive contribution confirming the diffusive behavior of the thin film. The exchange current density of the deposited film is calculated which is found to have higher value than that of bare FTO. I–V characteristics of WO3 are compared with that of bare FTO which reveals the smaller resistance offered by WO3 film. The equivalent circuit as obtained from Nyquist plot is used to estimate the resistance of electrolyte, film and charge transfer resistance along with the double-layer capacitance and Warburg impedance. Further, bode plot is analyzed to study the phase shift and thus the diffusive behavior of the material. [ABSTRACT FROM AUTHOR]

The structural role of an oxide as a former and modifier can have significant effects on the chemical durability and mechanical properties of the glass. Some oxides with high‐field strength cations, for example, MgO and ZrO2, are often labeled as a third group—intermediate, due to their either undetermined or dual structural roles dependent on the glass compositions. Based on our recent modification of the Makishima–Mackenzie (MM) model using the rigid‐unit Packing Fraction (RUPF), we analyzed a series of novel zirconia‐containing bioactive glasses. The RUPF‐based MM‐model provides better prediction of the elastic moduli of these new glasses in comparison to experimental measurements. At the same time, the structural role of zirconia can be determined by comparison with calculations by assuming various structural roles and those from experiments. We reveal that ZrO2 acts as the network former in phosphosilicate glasses, which leading to significant increase in packing fraction and consequent increase in Young's modulus. The recent experimental and atomistic simulation results support the glass former role of zirconia in silicate glasses. This method is general and applicable to other oxides in glasses. [ABSTRACT FROM AUTHOR]

The structure of liquid lithium pyroborate, Li4B2O5 (J = Li/B = 2), has been measured over a wide temperature range by high‐energy X‐ray diffraction, and compared to that of its glass and borate liquids of other compositions. The results indicate a gradual increase in tetrahedral boron fraction from 3(1)% to 6(1)% during cooling from T = 1271(15) to 721(8) K, consistent with the larger N4 = 10(1)% found for the glass, and literature 11B nuclear magnetic resonance measurements. van't Hoff analysis based on a simple boron isomerization reaction BØ3O2– ⇌ BØO22– yields ΔH = 13(1) kJ mol–1 and ΔS = 40(1) J mol–1 K–1 for the boron coordination change from 4 to 3, which are, respectively, smaller and larger than found for singly charged isomers for J ≤ 1. With these, we extend our model for N4(J, T), nonbridging oxygen fraction fnbr(J, T), configurational heat capacity CPconf(J,T)$C_{\rm{P}}^{{\rm{conf}}}(J,T)$, and entropy Sconf(J, T) contributions up to J = 3. A maximum is revealed in CPconf(J,T=Tg)$C_{\rm{P}}^{{\rm{conf}}}(J,T = {T_{\rm{g}}})$ at J = 1, and shown semi‐quantitatively to lead to a corresponding maximum in fragility contribution, akin to that observed in the total fragilities by temperature‐modulated differential scanning calorimetry. Lithium is bound to 4.6(2) oxygen in the pyroborate liquid, with 2.7(1) bonds centered around 1.946(8) Å and 1.9(1) around 2.42(1) Å. In the glass, nLiO = 5.4(4), the increase being due to an increase in the number of short Li–O bonds. [ABSTRACT FROM AUTHOR]

A series of white light-emitting Ca6-xNa2Y2(SiO4)6Cl2:Gd3+ chlorapatite compounds were synthesized by liquid solid solution-based hydrothermal method. The structural, electronic and optical properties of synthesized chlorapatite were studied in detail. The X-ray diffraction (XRD) analysis confirms the formation of monoclinic structure with space group P21/c. Fourier transform infrared spectroscopy shows different modes of SiO4 tetrahedron, with no impurity peaks due to (OH) and (CO2) group. Theoretical calculations were done by B3LYP hybrid GGA approximation using density functional theory. The computational band gap value of 3.8 eV was calculated using 3 × 3 × 3 Monkhorst mesh, which satisfies the experimental value of 4.3 eV calculated by diffuse transmittance spectroscopy. The band gap value calculated by molecular orbital theory was found to be 4.01 eV, which satisfied the above results. Mulliken population analysis shows that Y bonds are more covalent in nature as compared to Ca and Na bonds. The photoluminescence emission peaks obtained at 468 nm, 482 nm, 492 nm, 549 nm and 661 nm are perceived due to 6G7/2 – 6DJ, 6G7/2 – 6IJ and 6PJ – 8S7/2 transitions in white region under 220 nm UV excitation. [ABSTRACT FROM AUTHOR]

Methylammonium (MA) lead trihalide perovskites, CH3NH3PbX3 (X = I, Br, Cl), have emerged as a new class of light-absorbing materials for photovoltaic applications, reaching efficiencies of 23% when implemented in solar cell heterojunctions. In particular, MAPbBr3 is a promising member with a large bandgap that gives rise to a high open circuit voltage. Here we present a structural study from neutron diffraction (ND) data of an undeuterated MAPbBr3 specimen, carried out to follow its crystallographic behaviour in the 2–298 K temperature range. Besides the known crystallographic phases, i.e. the high-temperature Pm 3 ¯ m cubic structure, the intermediate I4/mcm tetragonal symmetry and the low-temperature Pnma orthorhombic phase, we additionally identified, from a detailed sequential ND analysis, a novel intermediate phase within the 148.5–154.0 K temperature range as an orthorhombic Imma structure, early associated with a coexistence of phases. Moreover, our ND data allowed us to unveil the configuration of the organic MA units and their complete localization within the mentioned temperature range, thus improving the crystallographic description of this compound. The evolution with temperature of the H-bonds between the organic molecule and the inorganic cage is also followed. A deep knowledge of the crystal structure and, in particular, the MA conformation inside the perovskite cage seems essential to establish structure–property correlations that may drive further improvements. [ABSTRACT FROM AUTHOR]

A class of radial, polynomial cutoff functions f c n (r) for short-ranged pair potentials or related expressions is proposed. Their derivatives up to order n and n + 1 vanish at the outer cutoff r c and an inner radius r i , respectively. Moreover, f c n (r ≤ r i ) = 1 and f c n (r ≥ r c ) = 0. It is shown that the used order n can qualitatively affect results: stress and bulk moduli of ideal crystals are unavoidably discontinuous with density for n = 0 and n = 1, respectively. Systematic errors on energies and computing times decrease by 20–50% for Lennard-Jones with n = 2 or n = 3 compared to standard cutting procedures. Another cutoff function turns out beneficial to compute Coulomb interactions using the Wolf summation, which is shown to not properly converge when local charge neutrality is obeyed only in a stochastic sense. However, for all investigated homogeneous systems with thermal noise (ionic crystals and liquids), the modified Wolf summation, despite being infinitely differentiable at r c , converges similarly quickly as the original summation. Finally, it is discussed how to reduce the computational burden of numerically exact Monte Carlo simulations using the Wolf summation even when it does not properly converge. [ABSTRACT FROM AUTHOR]

Concrete structures in extremely cryogenic environments may be subject to dynamic loadings as a result of occasional accidents or terrorist attacks during the service life. Considering the cryogenic temperature effect and strain rate effect of each phase for concrete, a meso-scale numerical model of the concrete subjected to cryogenic temperature and dynamic loadings was presented in this study, which serves as a preliminary foundation for calculating and evaluating the performances of concrete structures at cryogenic temperature. Taking concrete cube as an example, the dynamic compressive behavior and strain rate effect of concrete specimens at cryogenic temperature from 20 °C to –160 °C were modelled and investigated. The numerical results indicate that the failure appearances and compressive strength are highly related to the cryogenic temperature and dynamic loadings. The compressive strength at cryogenic temperature is greater than that at ambient temperature, and the sensitivity of dynamic compressive strength to strain rate is enhanced at cryogenic temperature. Moreover, the absorbed energy and dynamic elastic modulus tend to increase with the decrease of temperature and increase of strain rate. According to the numerical results, an empirical formula on dynamic increase factor of compressive strength at cryogenic temperatures (CDIF T) was established. [ABSTRACT FROM AUTHOR]

The computational discovery and design of zeolites is a crucial part of the chemical industry. Finding highly accurate while computational feasible protocol for identification of hypothetical siliceous frameworks that could be targeted experimentally is a great challenge. To tackle this challenge, we trained neural network potentials (NNP) with the SchNet architecture on a structurally diverse database of density functional theory (DFT) data. This database was iteratively extended by active learning to cover not only low-energy equilibrium configurations but also high-energy transition states. We demonstrate that the resulting reactive NNPs retain DFT accuracy for thermodynamic stabilities, vibrational properties, as well as reactive and non-reactive phase transformations. As a showcase, we screened an existing zeolite database and revealed >20k additional hypothetical frameworks in the thermodynamically accessible range of zeolite synthesis. Hence, our NNPs are expected to be essential for future high-throughput studies on the structure and reactivity of siliceous zeolites. [ABSTRACT FROM AUTHOR]

The Landé or g-factors of charge carriers are decisive for the spin-dependent phenomena in solids and provide also information about the underlying electronic band structure. We present a comprehensive set of experimental data for values and anisotropies of the electron and hole Landé factors in hybrid organic-inorganic (MAPbI3, MAPb(Br0.5Cl0.5)3, MAPb(Br0.05Cl0.95)3, FAPbBr3, FA0.9Cs0.1PbI2.8Br0.2, MA=methylammonium and FA=formamidinium) and all-inorganic (CsPbBr3) lead halide perovskites, determined by pump-probe Kerr rotation and spin-flip Raman scattering in magnetic fields up to 10 T at cryogenic temperatures. Further, we use first-principles density functional theory (DFT) calculations in combination with tight-binding and k ⋅ p approaches to calculate microscopically the Landé factors. The results demonstrate their universal dependence on the band gap energy across the different perovskite material classes, which can be summarized in a universal semi-phenomenological expression, in good agreement with experiment. The Landé factors govern all the spin-related basic phenomena and are the key parameters which guide spintronics applications. Here, Kirstein et al. demonstrate a universal dependence of the Landé factors on the bandgap energy of several perovskite materials. [ABSTRACT FROM AUTHOR]

The current study diligently analyzes the physical characteristics of halide perovskites AGeF3 (A = K, Rb) under hydrostatic pressure using density functional theory. The goal of this research is to reduce the electronic band gap of AGeF3 (A = K, Rb) under pressure in order to improve the optical characteristics and assess the compounds' suitability for optoelectronic applications. The structural parameters exhibit a high degree of precision, which correlates well with previously published work. In addition, the bond length and lattice parameters decrease significantly leading to a stronger interaction between atoms. The bonding between K(Rb)–F and Ge–F reveal ionic and covalent nature, respectively, and the bonds become stronger under pressure. The application of hydrostatic pressure demonstrates remarkable changes in the optical absorption and conductivity. The band gap becomes lower with the increment of pressure, resulting in better conductivity. The optical functions also predict that the studied materials might be used in a variety of optoelectronic devices operating in the visible and ultraviolet spectrum. Interestingly, the compounds become more suitable to be used in optoelectronic applications under pressure. Moreover, the external pressure has profound dominance on the mechanical behavior of the titled perovskites, which make them more ductile and anisotropic. [ABSTRACT FROM AUTHOR]

The previously unattained fabrication of single phase Ln2ZrO5 (Ln = Sm, Eu, Gd, and Tb) compounds via relatively low sintering temperature (1400°C) is achieved in this study using a coprecipitation method. The crystal structures have been investigated by neutron, synchrotron X‐ray powder diffraction, and electron diffraction techniques. While the general long‐range structure may be well described by the defect‐fluorite type structure with Fm3¯$\bar{3}$m symmetry, electron diffraction has highlighted a complex underlying modulated structure that varies between each compound. These compounds have been tested for ion‐irradiation response using in situ 1 MeV krypton ions and transmission electron microscopy characterization. None of the compounds undergo a crystalline to amorphous transition, even holding at 50 K. Both the underlying fluorite and modulated superstructures are little affected by the irradiation. However, some atomic rearrangements are observed in the postirradiated electron diffraction patterns for the Sm2ZrO5 specimen. [ABSTRACT FROM AUTHOR]

The use of Al for replacing high-cost alloying metals, like Ag, Bi, and Cu, as the second major element in Sn-based alloys, arises as a promising alternative for the development of low-cost Pb-free solder alloys. To date, however, the interfacial characteristics of Sn–Al solder joints in electronic substrates remain barely explored. Thus, the present study focuses on an understanding of the mechanisms affecting the heat transfer efficiency between a Sn–Al eutectic alloy and two types of substrates, establishing correlations with the microstructure evolution. Results of solidification experiments coupled with mathematical modeling demonstrate an interfacial thermal conductance between the Ni substrate and the Sn-0.5mass%Al alloy higher than that observed for the Sn–Al/Cu couple. Furthermore, Al-rich intermetallics are shown to occur at the interfacial reaction layers for both tested conditions. While dendritic and dendritic/cellular morphologies predominate in the solidification of the Sn–Al eutectic alloy in a Cu substrate, the better heat extraction through the Ni substrate induces the growth of refined high-cooling rate cells. Then, growth laws relating the length scale of the Sn-matrix, represented by cellular or primary dendritic spacings, to solidification thermal parameters such as cooling rate and growth rate are proposed. [ABSTRACT FROM AUTHOR]

Environmental barrier coatings (EBCs) will be needed to protect SiC‐based ceramic matrix composite components for the next generation of high‐efficiency industrial gas turbines (IGTs). The IGT application will require ≥25 kh lifetimes, and little data are available on EBC failure mechanisms, particularly at ≥1300°C. Initial 1‐h furnace cycle testing at 1350°C in 90 vol% H2O/10 vol% air was conducted ≥1000 cycles on thermally sprayed ytterbium disilicate (YbDS) coatings with and without an Si bond coating. By ≥1000 h, both EBCs formed thick, highly cracked, and fully crystalline cristobalite scales. Comparison of thermally grown oxide (TGO) microstructure and kinetics to isothermal rates of Si and SiC steam oxidation indicated a departure from slow‐growing parabolic growth to more rapid rates of silica formation. Possible mechanisms and implications for this acceleration are discussed. [ABSTRACT FROM AUTHOR]

We report a molecular modeling paradigm to describe silica polymerization reactions in aqueous solutions at conditions that are representative of realistic experimental processes like biosilicification or porous silica synthesis – i.e. at close to ambient temperatures and over a wide range of pH. The key point is to describe the Si-O-Si chemical bond formation and breakage processes through a continuous potential with a balance between attractive and repulsive interactions between suitably placed virtual sites and sticky particles. The simplicity of the model, its applicability in standard parallelized molecular dynamics codes, and its compatibility with the widely used MARTINI coarse-grained force-field allows for the study of systems containing millions of atoms over microsecond time scales. The model is calibrated to match experimental results for the temporal evolution of silica polymerization in aqueous solution close to the isoelectric point, and can describe silica polymerization and self-assembly processes during encapsulation of a surfactant micelle. [ABSTRACT FROM AUTHOR]

Objectives: A mechanical metamaterial is introduced herein by drawing inspiration from an Aztec geometric pattern. This metamaterial deformation mechanism for Poisson's ratio and Young's modulus is based on non-rotating rhombi with rotating triangles, while the shear modulus analysis herein is based on rotating rhombi with non-rotating triangles, hence 'partially rotating rigid units'. Methods: The coefficient of thermal expansion was obtained by equating the potential energy expressions from the simple harmonic motion and from the principle of energy equipartition, while the effective-moduli were acquired by equating the strain energy from rotational stiffness with that from the strain energy of deformation based on an assumed homogenized continuum. Due to the zero and extreme Poisson's ratio based on infinitesimal deformation, the finite approach was employed. Results: Results indicate that the proposed metamaterial exhibits anisotropic negative thermal expansion with sign-switching Poisson's ratio when applied stress along one axis is reversed. The Poisson's ratio for loading in another axis is undefined under tension but can be programmed to exhibit either sign when compressed. The Young's and shear moduli are directly governed by the rotational stiffness and strongly influenced by the extent of rotation, followed by the aspect ratio of the rotating units. Conclusion: Due to its uniqueness, the currently considered mechanical metamaterial can be used under specific requirements which are difficult to be attained by other materials with negative properties. [ABSTRACT FROM AUTHOR]

Al-Ni alloys (for Ni < 45 at.%) show a unique property in that, over at least part of the accessible undercooling range, the recalescence velocity measured in electromagnetically levitated samples is observed to decrease as the undercooling increases. This result has been subject to careful validation, including microgravity experiments utilising the TEMPUS levitation facility on-board the International Space Station (ISS). In these experiments, anomalous growth is observed to coincide with a recalescence morphology comprising multiple circular growth fronts [Herlach et al. Phys. Rev. Mat. 3, 073,402 (2019)], termed “scales”. In this paper we present an analysis of high speed video data from the ISS experiments in which we show that such scale-like growth is consistent with a recalescence front that is initially confined to a thin layer on the surface of the sample. This then nucleates a slower, radial inward growth, which is consistent with microstructures observed in Al-Ni droplets. We show that such surface recalescence would be favoured for samples which were surface enriched in Ni, wherein the recalescence velocity (at fixed nucleation temperature) increases rapidly with Ni-concentration. Moreover, it is shown that the anomalous velocity behaviour can be matched in all compositions studied if the surface enhancement in Ni is a linear function of the nucleation temperature with a gradient of 0.03 at.% K−1. Analysis of historical results from the literature indicates that such surface Ni-enhancement may have been present, but overlooked, in other experiments on Al-rich Al-Ni droplets. [ABSTRACT FROM AUTHOR]

Hybrid halide perovskite semiconductors exhibit complex, dynamical disorder while also harboring properties ideal for optoelectronic applications that include photovoltaics. However, these materials are structurally and compositionally distinct from traditional compound semiconductors composed of tetrahedrally coordinated elements with an average valence electron count of silicon. The additional dynamic degrees of freedom of hybrid halide perovskites underlie many of their potentially transformative physical properties. Neutron scattering and spectroscopy studies of the atomic dynamics of these materials have yielded significant insights into their functional properties. Specifically, inelastic neutron scattering has been used to elucidate the phonon band structure, and quasi-elastic neutron scattering has revealed the nature of the uncorrelated dynamics pertaining to molecular reorientations. Understanding the dynamics of these complex semiconductors has elucidated the temperature-dependent phase stability and origins of defect-tolerant electronic transport from the highly polarizable dielectric response. Furthermore, the dynamic degrees of freedom of the hybrid perovskites provide additional opportunities for application engineering and innovation. [ABSTRACT FROM AUTHOR]

The quantity of sewage sludge generated daily by wastewater treatment plants represents a major environmental problem and a financial burden for plant operators. Valorization strategies focusing on reusing sewage sludge as a raw material are currently developed. Vitrification can help us reduce the volume of waste and binds the components in the structure of chemically stable glasses and glass‐ceramics. In this study, the vitrification of sewage sludge inside a basaltic rock has been simulated by producing glasses and a glass‐ceramic from basalt enriched in calcium that lie between the stability fields of pyroxene and melilite in the system CaO–MgO–SiO2–Al2O3. CaO addition causes the oxidation of the melt at above the liquidus, increases the crystallization temperature, decreases the melting temperature, and improves the microhardness of the glasses. Glass‐ceramic processes improves the properties of the Ca‐doped basalt glass. The microhardness of the glass (8.2 GPa) and the glass‐ceramic (8.6 GPa) and leaching tests (in the ppb range) place both the glass and the glass‐ceramics at the high end of the mechanical properties and chemical resistance of ceramic tiles for the building industry. [ABSTRACT FROM AUTHOR]

The current generation of multilayer Si/Yb2Si2O7 environmental barrier coatings (EBCs) are temperature limited by the melting point of Si, 1414°C. To investigate higher temperature EBCs, the cyclic steam oxidation of EBCs comprised of a single layer of ytterbium disilicate (YbDS) was compared to multilayered Si/YbDS EBCs, both deposited on SiC substrates using atmospheric plasma spray. After 500 1‐h cycles at 1300°C in 90 vol%H2O‐10 vol%air with a gas velocity of 1.5 cm/s, both multilayer Si/YbDS and single layer YbDS grew thinner silica scales than bare SiC, with the single layer YbDS forming the thinnest scale. Both coatings remained fully adherent and showed no signs of delamination. Silica scales formed on the single layer coating were significantly more homogeneous and possessed a markedly lower degree of cracking compared to the multilayered EBC. The single layer EBC also was exposed at 1425°C in steam with a gas velocity of 14 cm/s in an alumina reaction tube. The EBC reduced specimen mass loss compared to bare SiC but formed an extensive 2nd phase aluminosilicate reaction product. A similar reaction product was observed to form on some regions of the bare SiC specimen and appeared to partially inhibit silica volatilization. The 1425°C steam exposures were repeated with a SiC reaction tube and no 2nd phase reaction product was observed to form on the single layer EBC or bare SiC. [ABSTRACT FROM AUTHOR]

The high‐temperature oxidation of additively manufactured and chemically vapor infiltrated (3D‐printed SiC) has been compared to chemical vapor deposited (CVD) SiC. 100‐h isothermal exposures were conducted at 1425° and 1300°C at 1 atm under both dry air and steam environments. A SiC reaction tube was utilized to reduce silica volatility. After steam oxidation at 1425° and 1300°C, on the 3D‐printed SiC surface, which was intrinsically rougher than the CVD surface, scales were 70%–90% thicker at the convex regions compared to concave/flat regions. In the convex regions, large cracks perpendicular to the oxidizing interface were observed. After dry air oxidation, scale thicknesses were comparable between 3D‐printed SiC and CVD SiC, regardless of geometry. Finite element modeling, conducted to elucidate the relationship between SiC geometry and ß‐ to α‐cristobalite transformation stress, determined cristobalite transformation tensile stresses to be on the order of 103 MPa during cool down, assuming a 6 vol% reduction. Compared to flat SiC substrates, tensile transformation stresses were elevated at concave regions and relaxed at convex regions. Combined with specimen mass gain (accounting for the rougher surface) of 3D‐printed SiC being 15%–32% higher for 3D‐printed SiC after 1300°C and 1425°C steam oxidation, the work presented concludes that the increased oxidation of 3D‐printed SiC is primarily caused by tensile hoop stresses driven by oxidation volume expansion. Lastly, the efficacy of the 3D‐printing method is demonstrated through the production of tristructural isotropic imbedded 3D‐printed SiC fuel forms. [ABSTRACT FROM AUTHOR]

Pyrochlores, with a general formula A2B2X7, are promising candidates in many potential applications due to their wide varieties of physical properties. Different combinations of cations and anions in the crystal structure enable the tailoring of their properties and functionalities. For cubic pyrochlores, the lattice constant, a, is an integrated result of stoichiometry, ionic radii, and electronegativities of alloying elements. It also has significant impacts on stabilities, electronic structures, ionic conductivities, and thus performance of materials. Here, we develop the Gaussian process regression model to shed light on the relationship among ionic radii, electronegativities, and lattice constants for cubic pyrochlores. The dataset includes ternary pyrochlores and mixed pyrochlores with co‐doping and multi‐doping situations. One hundred and thirty‐nine samples with lattice constants between 9.287 and 11.150 Å are examined. The model is highly stable and accurate that contributes to efficient and low‐cost lattice constant estimations. [ABSTRACT FROM AUTHOR]

In the present investigation, the feasibility of detecting the bromochlorodifluoromethane (BCF) gas molecule onto the outer surface of pristine single-wall silicon carbide nanotube (SiCNT), as well as its germanium-doped structures (SiCGeNT), was carefully evaluated. For achieving this goal, a density functional theory level of study using the Perdew, Burke, and Ernzerhof exchange-correlation (PBEPBE) functional together with a 6-311G(d) basis set has been used. Subsequently, the B3LYP, CAM-B3LYP, ωB97XD, and M06-2X functionals with a 6-311G(d) basis set were also employed to consider the single-point energies. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) were implemented by using the PBEPBE/6-311G(d) method, and the results were compatible with the electronic properties. In this regard, the total density of states (TDOSs), the Wiberg bond index (WBI), natural charge, natural electron configuration, donor-acceptor natural bond orbital interactions, and the second-order perturbation energies are performed to explore the nature of the intermolecular interactions. All of the energy calculations and population analyses denote that by adsorping of the gas molecule onto the surface of the considered nanostructures, the intermolecular interactions are of the type of strong physical adsorption. The doped nanotubes have a very high adsorption energy compared with pristine nanotube. Generally, it was revealed that the sensitivity of the adsorption will be increased when the gas molecule interacts with decorated nanotubes and decrease the HOMO-LUMO band gap; therefore, the change of electronic properties can be used to design suitable nanosensors to detect BCF gas. [ABSTRACT FROM AUTHOR]

Thermodynamic properties (heat capacity Cp, entropy S°, enthalpy change ΔH° and reduced Gibbs energy ΔΦ°) of crystalline WO3 in a temperature range of 80–1256 K were refined using two complementary calorimetric methods, namely differential scanning calorimetry and adiabatic vacuum calorimetry. Enthalpy changes during a number of successive phase transitions in WO3 were calculated from differential scanning calorimetry data in both heating and cooling regimes and compared to previously reported values. For the first time, enthalpy changes for the orthorhombic to monoclinic and monoclinic to tetragonal high-temperature phase transitions in WO3 were estimated. [ABSTRACT FROM AUTHOR]