Search

The spontaneous exchange bias effect (SEB) has wide application prospects in information storage technologies. In this study, nanoscale raw materials were used to fabricate antiferromagnetic Fe3BO6 polycrystals. The obtained Fe3BO6 exhibited a large SEB effect, where the value of the spontaneous exchange bias field at room temperature was as large as ∼4234 Oe. The room-temperature training effect, temperature-dependence, and maximum field-dependence of the HSEB were investigated. We propose that this giant SEB originates from the exchange-coupling interactions between the weak ferromagnetic surface state and the bulk antiferromagnetic state. The theoretical analysis results were further verified by comparing the magnetic properties of the Fe3BO6 with relatively low crystallinity. The results of this investigation will help find promising candidate materials for devices based on the SEB effect. [ABSTRACT FROM AUTHOR]

In this study, a fluorocarbon chain was grafted on the surface of the alumina insulator through the molecule self-assembly of perfluorododecyl trichlorosilane to enhance the vacuum surface flashover voltage. A hydrocarbon chain with the same molecular structure, devoid of fluorine element, was also grafted through the self-assembly of dodecyl trichlorosilane to enable comparison. The surface state examination of the self-assembled alumina insulators shows that both the molecules are attached to the alumina surface. The arrangement of the molecules on the surface is regular. Surface property tests reveal that the fluorocarbon chain endows the surface of alumina with a lower secondary electron emission yield and a lower gas adsorption volume than the hydrocarbon chain. Correspondingly, the surface flashover voltage of the fluorocarbon chain grafted insulator is higher than that of the hydrocarbon chain. This implies that the surface flashover voltage can be improved through surface fluorination, which converts hydrocarbon bonds to fluorocarbon bonds. The study demonstrates this possibility at the molecule level. [ABSTRACT FROM AUTHOR]

Three-dimensional topological semimetals are a class of electronic materials in which their bulk and surface states contain linear band touching nodes near the Fermi level. Like semiconductors, their properties will be affected by point and extended defects in their crystal structures, although the extent to which defects and disorders influence topological semimetals may differ in key ways due to their unique electronic structures. In this Tutorial, we provide an overview of the defects in topological semimetals, covering both computational and experimental methods for exploring defect-property relationships. We also include a discussion on open questions that still need to be explored further. [ABSTRACT FROM AUTHOR]

For the computation of vibrationally resolved electronic spectra, various approaches can be employed. Adiabatic approaches simulate vibronic transitions using harmonic potentials of the initial and final states, while vertical approaches extrapolate the final state potential from the gradients and Hessian at the Franck–Condon point, avoiding a full exploration of the potential energy surface of the final state. Our implementation of the vertical Hessian (VH) method has been validated with a benchmark set of four small molecules, each presenting unique challenges, such as complex topologies, problematic low-frequency vibrations, or significant geometrical changes upon electronic excitation. We assess the quality of both adiabatic and vertical approaches for simulating vibronic transitions. For two types of donor–acceptor compounds with promising thermally activated delayed fluorescence properties, our computations confirm that the vertical approaches outperform the adiabatic ones. The VH method significantly reduces computational costs and yields meaningful emission spectra, where adiabatic models fail. More importantly, we pioneer the use of the VH method for the computation of rate constants for non-radiative processes, such as intersystem crossing and reverse intersystem crossing along a relaxed interpolated pathway of a donor–acceptor compound. This study highlights the potential of the VH method to advance computational vibronic spectroscopy by providing meaningful simulations of intricate decay pathway mechanisms in complex molecular systems. [ABSTRACT FROM AUTHOR]

We simulate the photodynamics of gas-phase cyclobutanone excited to the S2 state using fewest switches surface hopping (FSSH) dynamics powered by time-dependent density functional theory (TDDFT). We predict a total photoproduct yield of 8%, with a C3:C2 product ratio of 0 trajectories to 8 trajectories. One primary S2 → S1 conical intersection is identified involving the compression of an α-carbon–carbon–hydrogen bond angle. Excited state lifetimes computed with respect to electronic state populations were found to be 3.96 ps (S2 → S1) and 498 fs (S1 → S0). We also generate time-resolved difference pair distribution functions (ΔPDFs) from our TDDFT-FSSH dynamics results in order to generate direct comparisons with ultrafast electron diffraction experiment observables. Global and target analysis of time-resolved ΔPDFs produced a distinct set of lifetimes: (i) a 0.548 ps decay and (ii) a 1.69 ps decay, both resembling the S2 minimum, as well as (iii) a long decay that resembles the S1 minimum geometry and the fully separated C2 products. Finally, we contextualize our results by considering the impact of the most likely sources of significant errors. [ABSTRACT FROM AUTHOR]

Vibrational coherences in ultrafast pump–probe (PP) and 2D electronic spectroscopy (2DES) provide insights into the excited state dynamics of molecules. Femtosecond coherence spectra and 2D beat maps yield information about displacements of excited state surfaces for key vibrational modes. Half-broadband 2DES uses a PP configuration with a white light continuum probe to extend the detection range and resolve vibrational coherences in the excited state absorption (ESA). However, the interpretation of these spectra is difficult as they are strongly dependent on the spectrum of the pump laser and the relative displacement of the excited states along the vibrational coordinates. We demonstrate the impact of these convoluting factors for a model based upon cresyl violet. A careful consideration of the position of the pump spectrum can be a powerful tool in resolving the ESA coherences to gain insights into excited state displacements. This paper also highlights the need for caution in considering the spectral window of the pulse when interpreting these spectra. [ABSTRACT FROM AUTHOR]

MoS2 has generated significant attention due to its unique electronic properties and versatile applications. Being a van der Waals material, MoS2 is expected to exhibit an inert surface due to lack of dangling bond. However, our photoemission study finds MoS2 to be highly sensitive toward residual gases. The position of the valence band maximum (VBM) shifts even in a vacuum of 10−10 Torr. We find this to be due to CO adsorption causing unintentional electron doping. The time evolution of the position of VBM is exponential, and it reaches two different saturation points, depending on whether the sample is exposed to ultraviolet (UV) radiation or not. Our XPS (x-ray photoemission spectroscopy) study shows no time-dependent escape of sulfur, which was in a previous study attributed to a VBM shift. The VBM shift can be reversed by annealing, sputtering, and UV light, which desorb CO gases. The study shows that the MoS2 surface is easily doped, which offers the possibility of using it as a sensor but in many other applications could diminish device performance and needs to be considered. [ABSTRACT FROM AUTHOR]

MoS2 has generated significant attention due to its unique electronic properties and versatile applications. Being a van der Waals material, MoS2 is expected to exhibit an inert surface due to lack of dangling bond. However, our photoemission study finds MoS2 to be highly sensitive toward residual gases. The position of the valence band maximum (VBM) shifts even in a vacuum of 10−10 Torr. We find this to be due to CO adsorption causing unintentional electron doping. The time evolution of the position of VBM is exponential, and it reaches two different saturation points, depending on whether the sample is exposed to ultraviolet (UV) radiation or not. Our XPS (x-ray photoemission spectroscopy) study shows no time-dependent escape of sulfur, which was in a previous study attributed to a VBM shift. The VBM shift can be reversed by annealing, sputtering, and UV light, which desorb CO gases. The study shows that the MoS2 surface is easily doped, which offers the possibility of using it as a sensor but in many other applications could diminish device performance and needs to be considered. [ABSTRACT FROM AUTHOR]

Dynamic responses of copper titanates to alternating electric fields with different strengths are characterized in terms of dielectric spectrums. This work extends the introduction of quasipolaron surface polarization (QSP). A collective of quasipolarons pinned at grain surfaces is involved in the electric polarization, which is confirmed by the quadratic polarization–permittivity relation. Because electric polarization is a macroscopic quantum effect, the QSP is described in terms of the density of states (DOS). As a sign of reverse ferroelectricity, dielectric hysteresis loops of reverse-S shape reveal that the characteristic remnant polarization is proportional to the DOS ratio of quasipolaron surface excited to ground states. Although the DOS of the surface ground state is dependent on the mole ratio of quasipolaron quantity, both the DOS and the energy levels of surface excited states show the intrinsic angular-frequency dependence in a power function manner. [ABSTRACT FROM AUTHOR]

The small-signal equivalent circuit of GaN-based self-switching diodes has been obtained, which apart from the intrinsic R ‖ C branch, generally used to describe the diode performance, needs new elements to describe the low-frequency dispersion of the impedance originated by the presence of surface and bulk traps. The proposed model allows us to reproduce not only the high-frequency results (extracted from S-parameter measurements in the 40 MHz–43.5 GHz range) at room temperature, but also the low-frequency impedance measurements (75 kHz–30 MHz) at cryogenic temperatures down to 70 K. These new elements are a self-inductance associated to the effect of surface states (typical of a device with a high surface-to-volume ratio) and an extra series R – C branch modeling the influence of the bulk traps. [ABSTRACT FROM AUTHOR]

In quantum chemical calculations of heterogeneous structures in solids, e.g., when an impurity is located on the surface, the conventional cluster model is insufficient to describe the electronic structure of substrates due to its finite size. The open-boundary cluster model (OCM) overcomes this problem by performing cluster calculations under the outgoing-wave boundary condition. In this method, a complex absorbing potential (CAP) is used to impose the boundary condition, but the CAP used in the previous studies required parameter optimization based on the complex variational principle. This study proposes and applies a parameter-free CAP to OCM calculations. This approach makes it possible to uniquely determine the band-specific CAP based on the surface Green's function theory. Using this CAP, we conducted OCM calculations of the tight-binding model of a one-dimensional semi-infinite chain, and we found that the calculated density of states agreed with the exact one. Surface states of the Newns–Anderson–Grimley model were also computed using the CAP, and the projected density of states on the adsorbed atom was successfully reproduced. [ABSTRACT FROM AUTHOR]

Photocatalytic water splitting for green hydrogen production is hindered by the sluggish kinetics of oxygen evolution reaction (OER). Loading a co-catalyst is essential for accelerating the kinetics, but the detailed reaction mechanism and role of the co-catalyst are still obscure. Here, we focus on cobalt oxide (CoOx) loaded on bismuth vanadate (BiVO4) to investigate the impact of CoOx on the OER mechanism. We employ photoelectrochemical impedance spectroscopy and simultaneous measurements of photoinduced absorption and photocurrent. The reduction of V5+ in BiVO4 promotes the formation of a surface state on CoOx that plays a crucial role in the OER. The third-order reaction rate with respect to photohole charge density indicates that reaction intermediate species accumulate in the surface state through a three-electron oxidation process prior to the rate-determining step. Increasing the excitation light intensity onto the CoOx-loaded anode improves the photoconversion efficiency significantly, suggesting that the OER reaction at dual sites in an amorphous CoOx(OH)y layer dominates over single sites. Therefore, CoOx is directly involved in the OER by providing effective reaction sites, stabilizing reaction intermediates, and improving the charge transfer rate. These insights help advance our understanding of co-catalyst-assisted OER to achieve efficient water splitting. [ABSTRACT FROM AUTHOR]

Fabrication of modern solid-state devices demands precise control of shape and dimensions, which requires an accurate knowledge of the role that surfaces play in such devices. To contribute to the understanding of surface effects on silicon nanowires, we present an atomistic study of the electronic properties of silicon nanostructures exhibiting surface facets over the (100) , (110) , (111) , and (112) crystallographic planes. We calculate the electronic structure of slabs in such a way that the effect of individual facets may be observed. Subsequently, we determine the electronic structure of nanowires grown along the [ 100 ] , [ 110 ] , [ 111 ] , and [ 112 ] directions, with surfaces defined by a combination of the mentioned facets. Our nanowires comprise diameters ranging from 1 to 6.7 nm and structures with more than 1000 atoms. We discuss the band structure, the relation between direct and indirect bandgaps, and the density of states. We base our calculations on semiempirical pseudopotentials where we implement complex potentials to describe passivants. We find that there is a transition from direct to indirect gap for the [ 111 ] direction at approximately 2 nm and that the difference between the direct and indirect gap may reach more than 300 meV depending on the diameter. We show that the occurrence of a direct bandgap is favored by the presence of the (100) facet and that it is related to a higher surface density of states. Conversely, we find that the (111) facet is the most inert surface type with a lower surface density of states. [ABSTRACT FROM AUTHOR]

We study theoretically the electronic structure of three-dimensional (3D) higher-order topological insulators in the presence of step edges. We numerically find that a 1D conducting state with a helical spin structure, which also has a linear dispersion near the zero energy, emerges at a step edge and on the opposite surface of the step edge. We also find that the 1D helical conducting state on the opposite surface of a step edge emerges when the electron hopping in the direction perpendicular to the step is weak. In other words, the existence of the 1D helical conducting state on the opposite surface of a step edge can be understood by considering an addition of two different-sized independent blocks of 3D higher-order topological insulators. On the other hand, when the electron hopping in the direction perpendicular to the step is strong, the location of the emergent 1D helical conducting state moves from the opposite surface of a step edge to the dip (270 ° edge) just below the step edge. In this case, the existence at the dip below the step edge can be understood by assigning each surface with a sign (+ or −) of the mass of the surface Dirac fermions. These two physical pictures are connected continuously without the bulk bandgap closing. Our finding paves the way for on-demand creation of 1D helical conducting states from 3D higher-order topological insulators employing experimental processes commonly used in thin-film devices, which could lead to, e.g., a realization of high-density Majorana qubits. [ABSTRACT FROM AUTHOR]

We investigate the finite size effects of a three-dimensional second-order topological insulator with fourfold rotational symmetry and time-reversal symmetry. Starting from the effective Hamiltonian of the three-dimensional second-order topological insulator, we derive the effective Hamiltonian of four two-dimensional gapped surface states by perturbative methods. Then, the sign alternation of the mass term of the effective Hamiltonian on the adjacent surface leads to the hinge state. In addition, we obtain the effective Hamiltonian and its wave function of one-dimensional gapless hinge states with semi-infinite boundary conditions based on the effective Hamiltonian of two-dimensional surface states. In particular, we find that the hinge states on the two sides of the same surface can couple to produce a finite energy gap. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel network‐based approach for reconstructing signed distance functions from fluid particles. The method uses a weighting kernel to transfer particles to a regular grid, which forms the input to a convolutional neural network. We propose a regression‐based regularization to reduce surface noise without penalizing high‐curvature features. The reconstruction exhibits improved spatial surface smoothness and temporal coherence compared with existing state of the art surface reconstruction methods. The method is insensitive to particle sampling density and robustly handles thin features, isolated particles, and sharp edges. [ABSTRACT FROM AUTHOR]

Li2S–P2S5–LiI-type solid electrolytes, such as Li4PS4I, Li7P2S8I, and Li10P3S12I, are promising candidates for anode layers in all-solid-state batteries because of their high ionic conductivity and stability toward Li anodes. However, few studies have been conducted on their detailed local structure and particle surface state. In this study, Li7P2S8I (Li2S: P2S5:LiI = 3:1:1) solid electrolytes as the chemical composition were synthesized by mechanical milling and liquid-phase shaking, and their local structures were analyzed by transmission electron microscopy. The particle surface states were analyzed by X-ray photoelectron spectroscopy, high-energy X-ray scattering measurements, and neutron total scattering experiments. The results showed that Li7P2S8I solid electrolytes are composed of nanocrystals, such as Li4PS4I, LiI, Li10P3S12I and an amorphous area as the main region, indicating that the crystalline components alone do not form ionic conductive pathways, with both the amorphous and crystalline regions contributing to the high ionic conductivity. Moreover, the ionic conductivity of the crystalline/amorphous interface of the glass-ceramic was higher than that of the Li2S–P2S5–LiI glass. Finally, an organic-solvent-derived stable surface layer, which was detected in the liquid-phase shaking sample, served as one of the factors that contributed to its high stability (which surpassed that of the mechanically milled sample) toward lithium anodes. We expect these findings to enable the effective harnessing of particle surface states to develop enhanced sulfide solid electrolytes. [ABSTRACT FROM AUTHOR]

This study focuses on the evolution of the fatigue strength of Laser Powder Bed Fusion (L‐PBF) produced Ti‐6Al‐4V as a function of the chemical etching finishing process. The aim is to identify the critical fatigue crack initiation mechanisms and the transitions between them in terms of the evolution of the surface micro‐geometry. This is done using three different geometries and six different surface states. The evolution of the crack initiation mechanisms is then used to explain the evolutions of the fatigue strength and the fatigue scatter. Chemical etching affects the fatigue life via a polishing effect, which directly influences both the finite and the high cycle fatigue domains. It is shown that chemical etching makes it possible to obtain fatigue strengths that are almost similar to those of the machined surface. However, it is also observed that etching cannot fully counteract the effects of large surface cavities caused by surface connected porosities. Highlights: Fatigue results are presented for Ti‐6Al‐4V L‐PBF with and without chemical etching.The fatigue strength sensitivity to defect size is clearly characterized.The different fatigue crack initiation mechanisms are identified.The initiation mechanisms evolution as a function of the finishing process is studied. [ABSTRACT FROM AUTHOR]

The optical properties of Carbon dot (CD) solution significantly change on dilution. Herein, the effect of dilution on the optical properties of folic acid-derived CD was meticulously analyzed using absorption and photoluminescence (PL) spectroscopy. Absorption spectra of as-prepared CD solution consist of four overlapping yet discernable absorption bands centered at ~ 249, 302, 348, and 330 nm, respectively, attributed to originate from the π-π* transition and n-π* transitions and/or surface states. As the CD solution is diluted from 100 to 5%, these four absorption bands become more resolved. Moreover, we observed a blueshift of ~ 30 nm for the transitions at ~ 302 nm due to surface state with dilution up to 20% CD concentration. This is attributed to the decrease in the interaction between surface states due to the increase in the interparticle distance with dilution. PL emission from the as-prepared CD solution is centered at 463 nm and is asymmetric. This can be resolved into three components centered at 446 nm (intense), 474 nm (intense) and 508 nm (weak) respectively. With dilution, the PL intensity corresponding to the 463 nm emission seems to increase up to an optimum concentration of 15% CD and then decreases. The high concentration effectively quenches the luminescence through inner filter effect which is evident from the overlapping of absorption peak with the peak in the excitation spectrum together with no notable change in the average decay time. The decrease in the percentage of overlapping area of the absorption and excitation spectra with dilution causes the reduction of inner filter effect and enhances the luminescence for diluted solutions. Furthermore, we found that the surface states become more dominant in the contribution of luminescence of CD, whose influence diminishes in extremely diluted solutions, thereby the intensity decrease below 15% dilution. [ABSTRACT FROM AUTHOR]

Hybrid-order topological insulators combine first- and higher-order topological properties and host topological boundary states with codimension one and more than one in different bandgaps. A Weyl semimetal (WSM) can possess two types of Weyl points: one class of Weyl points terminates the Fermi arc surface states, while another class of Weyl points not only launch Fermi arc surface states but also hinge arc states, exhibiting the hybrid-order topology. Here, we propose a hybrid-order WSM by stacking two-dimensional rhomboid lattices based on chiral nearest-neighbor and double-helix next-nearest interlayer couplings. The first type of Weyl point that only truncates the Fermi arc surface states exists at the crossing of any two-fold degeneracy of two adjacent bands, and the second type of Weyl point that connects the hinge arc states only appears at the crossing of the two middle bands. Our findings enrich the classification of topological semimetals in condensed matter physics. [ABSTRACT FROM AUTHOR]

Semiconductor heterojunctions have garnered extensive interest in photocatalytic hydrogen generation, yet the limited light absorption and charge transfer efficiencies still restrict the photocatalytic performance. The topological insulator has unique surface states and high‐mobility electrons, demonstrating the significant potential for enhancing photocatalysis. Herein, a ternary photocatalyst based on a topological insulator, in which CdS and ZnS nanoparticles are grown on Bi2Se3 nanotube, is prepared for efficient photocatalysis driven by topological surface state for the first time. Under simulated solar light irradiation, the CdS/ZnS/Bi2Se3 nanotubes display a robust photocatalytic hydrogen production rate of 7.13 mmol h−1 g−1, which is 69.2 times of CdS and comparable to many CdS‐based photocatalysts. The unique hollow structure, topological surface state of Bi2Se3, and cooperative bandgap excitations of the three components endow the hybrids with wide light response to harvest solar energy. Meanwhile, the multichannel charge transfer facilitated by topological surface state and internal electric fields within the hybrids effectively suppresses the recombination of the photogenerated charge carriers. This mechanism maintains a high concentration of stable electrons on Bi2Se3, resulting in highly efficient hydrogen production. This work provides a new inspiration for designing heterojunction photocatalysts based on topological insulators for high‐efficiency solar‐driven energy conversion. [ABSTRACT FROM AUTHOR]

Light‐driven dry reforming of methane is a promising and mild route to convert two greenhouse gas into valuable syngas. However, developing facile strategy to atomically‐precise regulate the active sites and realize balanced and stable syngas production is still challenging. Herein, we developed a spatial confinement approach to precisely control over platinum species on TiO2 surfaces, from single atoms to nanoclusters. The configuration comprising single atoms and sub‐nanoclusters engenders pronounced electronic metal‐support interactions, with resultant interfacial states prompting surface charge rearrangement. The unique geometric and electronic properties of these atom‐cluster assemblies facilitate effective activation of CH4 and CO2, accelerating intermediate coupling and minimizing side reactions. Our catalyst exhibits an outstanding syngas generation rate of 34.41 mol gPt−1 h−1 with superior durability, displaying high apparent quantum yield of 9.1 % at 365 nm and turnover frequency of 1289 h−1. This work provides insightful understanding for exploring more multi‐molecule systems at an atomic scale. [ABSTRACT FROM AUTHOR]

Developing transparent and efficient photoanodes is a challenging but essential task in tandem photoelectrochemical cell for unassisted solar water splitting without an external bias. Here we report construction of p–n homojunction hematite photoanodes by hybrid microwave annealing-induced single antimony doping, which results in the gradually-increased valence states from the surface to the inside by the unique features of hybrid microwave annealing. The Sb-doped p–n homojunction hematite photoanode exhibits improved performance and displays a good transparency, achieving a stable photocurrent density of ~4.21 mA cm−2 at 1.23 VRHE under 100 mW cm−2 solar irradiation, which is comparable to the reported state-of-the-art hematite photoanodes. More importantly, a parallel-connected stack of six photoanodes of transparent p–n homojunction records a near-theoretical photocurrent density of ~10 mA cm–2 at 1.23 VRHE under standard photoelectrochemical water splitting conditions, which serves as a useful reference for hematite photoanodes and promises its practical application for unbiased photoelectrochemical water splitting. Developing efficient and transparent photoanodes for solar water splitting is crucial for advancing clean energy technologies. Here, the authors report Sb-doped p–n homojunction hematite photoanodes that achieve high transparency and a stable photocurrent density of 4.21 mA cm–2. [ABSTRACT FROM AUTHOR]

Rich momentum-dependent electronic structure naturally arises in solids with long-range crystalline symmetry. Reliable and scalable quantum technologies rely on materials that are either not perfect crystals or non-crystalline, breaking translational symmetry. This poses the fundamental questions of whether coherent momentum-dependent electronic states can arise without long-range order, and how they can be characterized. Here we investigate Bi2Se3, which exists in crystalline, nanocrystalline, and amorphous forms, allowing direct comparisons between varying degrees of spatial ordering. Through angle-resolved photoemission spectroscopy, we show for the first time momentum-dependent band structure with Fermi surface repetitions in an amorphous solid. The experimental data is complemented by a model that accurately reproduces the vertical, dispersive features as well as the replication at higher momenta in the amorphous form. These results reveal that well-defined real-space length scales are sufficient to produce dispersive band structures, and that photoemission can expose the imprint of these length scales on the electronic structure. Recent studies showing dispersive surface states in an amorphous topological insulator has deepened the understanding of momentum-space electronic structure. Here the authors report dispersive electronic states and a distinct Fermi surface with Brillouin-zone-like repetitions in amorphous Bi2Se3. [ABSTRACT FROM AUTHOR]

Diamond-like carbon (DLC)/poly-α-olefin (PAO) composite system attracts much attention in reducing the tribo-induced risks for mechanical mobility systems and energy saving. However, the coupled effect of applied load and PAO viscosity on the tribological behavior of the DLC/PAO system, which normally causes the transition between different lubrication states of mated surfaces, and the corresponding synergistic mechanism remain unclear. Here, we fabricated the DLC/PAO composite system, and the evolutions of microstructure, morphologies, and tribological properties induced by both PAO viscosity and applied load were investigated systematically. Results indicated that under low applied load, the system with moderate PAO viscosity exhibited the best tribological performance, while the PAO with high viscosity was suggested with increasing the applied load. Moreover, the variations of PAO viscosity and applied load seriously affected the distribution and load-bearing capacity of oil, interfacial graphitization degree, and formation of lubricating oil film, which brought complicated effects on the tribological properties of composite systems. The present results guide the selection and design of an advanced DLC/PAO lubrication system according to the working conditions. [ABSTRACT FROM AUTHOR]

Topologically nontrivial Fe-based superconductors attract extensive attentions due to their ability of hosting Majorana zero modes (MZMs) which could be used for topological quantum computation. Topological defects such as vortex lines are required to generate MZMs. Here, we observe the robust edge states along the surface steps of CaKFe4As4. Remarkably, the tunneling spectra show a sharp zero-bias peak (ZBP) with multiple integer-quantized states at the step edge under zero magnetic field. We propose that the increasing hole doping around step edges may drive the local superconductivity into a state with possible spontaneous time-reversal symmetry breaking. Consequently, the ZBP can be interpreted as an MZM in an effective vortex in the superconducting topological surface state by proximity to the center of a tri-junction with different superconducting order parameters. Our results provide new insights into the interplay between topology and unconventional superconductivity, and pave a new path to generate MZMs without magnetic field. [ABSTRACT FROM AUTHOR]

In traditional stability analyses of three-dimensional slopes, soil has often been treated as a homogeneous material with single-parameter properties, overlooking the variability inherent in the strength parameters and unit weight of natural soil. This oversight can lead to an overestimation of slope stability and reliability. To address this issue, this manuscript introduces a novel approach. Initially, a horn-shaped double logarithmic spiral failure mechanism for three-dimensional slopes is constructed based on the kinematic approach within the framework of limit analysis theory. The critical height of the three-dimensional slope is calculated using the mean values of soil properties. Subsequently, the stochastic response surface method is employed to formulate a limit state equation for three-dimensional slopes, with three different algorithms utilized to analyze failure probability. Two cases are employed to validate the proposed method and to assess the efficiency and accuracy of the algorithms. Further, a back analysis of the probabilistic distribution of strength parameters for three-dimensional slopes is performed using the stochastic response surface limit state equation. The findings reveal that the relative width of the three-dimensional slope, the coefficient of variation (COV) of strength parameters, and unit weight significantly affect slope reliability. An increase in relative width leads to higher failure probability, while larger COV values for strength parameters and unit weight correspond to higher failure probability. Through back analysis, the results considering parameter variability align more closely with strength parameters obtained from in situ experiments. [ABSTRACT FROM AUTHOR]

Unidirectional spin Hall magnetoresistance (USMR) has emerged as a promising candidate for magnetoresistive random-access memory (MRAM) technology. However, the realization of high signal-to-noise output signal in USMR devices has remained a challenge, primarily due to the limited USMR effect at room temperature. In this study, we report a large USMR effect in FeNi/Pt/Bi₂Se₃ trilayers through interfacial engineering with Pt to optimize the spin current transmission efficiency and electron-magnon scattering. Our devices exhibit a USMR value that is an order of magnitude higher than previously reported systems, reaching 30.6 ppm/MA/cm² at room temperature. First-principles calculations and experimental observations suggest that the Pt layer not only preserves the spin-momentum locked topological surface states in Bi₂Se₃ at the Fermi-level but also generates additional Rashba surface states within the Pt itself to enhance the effective SOT efficiency. Furthermore, we demonstrate that the two-terminal USMR-MRAM devices show robust output performance with 2nd harmonic resistance variation around 0.11 Ω/mA. Remarkably, the performance of these devices further improves at elevated temperatures, highlighting their potential for reliable operation in a wide range of environmental conditions. Our findings pave the way for future advancements in high-performance, energy-efficient spintronic memory devices. Unidirectional spin Hall magnetoresistance refers to an asymmetric resistance response, which allows for the readout of the magnetic state from two terminal devices. Here, Zhang et al demonstrate a large unidirectional spin hall magnetoresistance FeNi/Pt/Bi₂Se₃ trilayers and present a robust random-access magnetoresistance device. [ABSTRACT FROM AUTHOR]

Topologically nontrivial Fe-based superconductors attract extensive attentions due to their ability of hosting Majorana zero modes (MZMs) which could be used for topological quantum computation. Topological defects such as vortex lines are required to generate MZMs. Here, we observe the robust edge states along the surface steps of CaKFe4As4. Remarkably, the tunneling spectra show a sharp zero-bias peak (ZBP) with multiple integer-quantized states at the step edge under zero magnetic field. We propose that the increasing hole doping around step edges may drive the local superconductivity into a state with possible spontaneous time-reversal symmetry breaking. Consequently, the ZBP can be interpreted as an MZM in an effective vortex in the superconducting topological surface state by proximity to the center of a tri-junction with different superconducting order parameters. Our results provide new insights into the interplay between topology and unconventional superconductivity, and pave a new path to generate MZMs without magnetic field. [ABSTRACT FROM AUTHOR]

Obstructed atomic insulator is recently proposed as an unconventional material, in which electric charge centers localized at sites away from the atoms. A half-filling surface state would emerge at specific interfaces cutting through these charge centers and avoid intersecting any atoms. In this article, we utilized photoemission spectroscopy and density functional theory calculations to study one of the obstructed atomic insulator candidates, NiP2. A floating surface state with large effective mass that is close to the Fermi level and isolated from all bulk states is resolved on the (100) cleavage plane, implying better catalytic activity in this plane than the previously studied surfaces. Density functional theory calculation results elucidate that this floating surface state is originated from the obstructed Wannier charge centers, albeit underwent surface reconstruction. Our findings not only shed lights on the study of obstructed atomic insulators, but also provide possible route for development of new catalysts. [ABSTRACT FROM AUTHOR]

Cr doping is a new strategy to enhance the OER (Oxygen Evolution Reaction) performance of NiFe-LDH (NiFe-Layered Double Hydroxides) by optimizing surface states and offering a scalable production process. However, as an additive element, Cr itself has weak OER performance, so its promotion on the Ni- and Fe-active site by electron perturbation and structural stabilization in NiFeCr-LDH has been the focus. Herein, a one-step hydrothermal method is used to incorporate Cr into NiFe-LDH, systematically investigating the relationship between Cr content and the material's microstructure. The results of physical characterization show that Cr ion plays a leading role in the electron perturbation Ni/Fe-active center, which causes the increasing of Fe3+ and Ni3+ content. Furthermore, variations in Cr content resulted in the lattice stretching and morphology evolving synchronously. The optimized NiFeCr-LDH exhibited significantly enhanced OER activity and durability compared to undoped NiFe-LDH and outperformed commercial RuO 2 catalysts. Additionally, a microstructure comparison was made between the initial- and long-term used-NiFeCr-LDH. The findings reveal that the material's distinctive structural evolution behavior confers it with exceptional self-adaptability to the OER reaction, which results in a consistent enhancement of activity lasting up to 12 h during long-term I-t test showing a new idea for the design of high performance NiFeCr-LDH. • A series of NiFeCr-LDH-x were designed to study Cr doping' optimal ratio and effect. • NiFeCr-LDH-0.36 has a 0.40% activity loss after 12 h of OER operation and a 0.2% change after 5000 C V cycles. • Cr' threshold effect affects the electrochemical properties and microstructure of catalyst. • The self-adaptation induced by Cr improves the activity and stability of the catalyst. [ABSTRACT FROM AUTHOR]

Failure probability function (FPF) can reflect quantitative effects of random input distribution parameter (DP) on failure probability, and it is significant for decoupling reliability‐based design optimization (RBDO). But the FPF estimation is time‐consuming since it generally requires repeated reliability analyses at different DPs. For efficiently estimating FPF, an augmented directional sampling (A‐DS) is proposed in this paper. By using the property that the limit state surface (LSS) in physical input space is independent of DP, the A‐DS establishes transformation of LSS samples in standard normal spaces corresponding to different DPs. By the established transformation in different standard normal spaces, the LSS samples obtained by DS at a given DP can be transformed to those at other DPs. After simple interpolation post‐processing on those transformed samples, the failure probability at other DPs can be estimated by DS simultaneously. The main novelty of A‐DS is that a strategy of sharing DS samples is designed for estimating the failure probability at different DPs. The A‐DS avoids repeated reliability analyses and inherits merit of DS suitable for solving problems with multiple failure modes and small failure probability. Compared with other FPF estimation methods, the examples sufficiently verify the accuracy and efficiency of A‐DS. [ABSTRACT FROM AUTHOR]

Corrosion processes are often discussed as stochastic events. Here, it is shown that some of these seemingly random processes are not driven by nanoscopic fluctuations but rather by the spatial distribution of micrometer‐scale heterogeneities that trigger fast reactions associated with corrosion. Using a novel excitable reaction‐diffusion model, corrosion waves traveling over the metal surface and the associated material loss are described. This resulting nonuniform corrosion penetration, seen as a height loss in modeling, exposes buried intermetallic particles, which depending on the local electrochemical state of the surface trigger or block new waves. Informed by quantitative experimental data for the Mg–Al–Zn alloy AZ31B, wave speeds, wave widths, and average material loss are accurately captured. Morphogenic mitigation based on wave‐breaking microparticles is also simulated. While AZ31B corrosion is identified as a process driven by rare‐wave events, this study predicts several other corrosion regimes that proceed via spots or patchy patterns, opening the door for new protection, design, and prediction strategies. [ABSTRACT FROM AUTHOR]

The electronic intrinsic surface states in wurtzite Zn-IV-N2 (with group- IV = Sn , Ge and Si) semiconductors were investigated using an intermediate-coupling variational approach considering the electron–surface optical phonon interaction influence. The intrinsic surface state energy distribution and the average penetrating depth of surface state eigen-wave function of the electron have been evaluated numerically by changing the surface potential barrier V 0 for wurtzite ZnSnN2, ZnGeN2 and ZnSiN2, respectively. The results show that the electronic intrinsic surface state energy increased linearly with increasing surface potential barrier V 0 for all the calculated materials. The result also indicated that the electronic intrinsic surface state energies variations due to the influence of electron–surface optical phonon interaction are dozens of meV. The average penetrating depth of electronic surface state eigen-wave function is independent of V 0 . Its value is no more than the corresponding material's lattice constant. The electronic scattering by surface optical phonon should be taken into account in the study of the intrinsic surface state of electrons in the group of Zn-IV-nitrides (with IV = Sn , Ge and Si) semiconductors, especially for materials having strong electron–phonon interaction and wide band gap. [ABSTRACT FROM AUTHOR]

In the pickling process and acidizing program for oil wells, the acidic corrosion of metals is a problem that needs to be addressed. Various acid corrosion inhibitors have been studied and used to mitigate the acidic corrosion of carbon steel. In this paper, the corrosion inhibition of 2‐aminobenzothiazole (2 N‐BT), 2‐amino‐4‐hydroxybenzothiazole (2 N4O‐BT), and 2‐amino‐6‐hydroxybenzothiazole (2 N6O‐BT) on carbon steel in 0.5 mol/L HCl was investigated using electrochemical and quantum chemical methods. All three molecules exhibited corrosion inhibition effects. Compared to 2 N‐BT, 2 N4O‐BT and 2 N6O‐BT showed less sensitivity to the environmental conditions and the surface state of the metal. Among them, 0.0010 mol/L 2 N6O‐BT demonstrated the highest and most persistent corrosion inhibition, exhibiting a mixed inhibition mechanism with cathodic inhibition dominance. The adsorption of 2 N6O‐BT on the carbon steel surface was found to be non‐uniform, preferentially adsorbing at certain active sites on the surface, following Freundlich‐Langmuir thermodynamic characteristics. It showed initial strongly adsorbed points and weakly adsorbed regions. With continued adsorption of 2 N6O‐BT, the differences between strongly adsorbed points and weakly adsorbed regions decreased. The introduction of hydroxyl groups, especially in 2 N6O‐BT, extended the negative potential region and enhanced the coordination activity of the molecule, generating the orbital distribution that was advantageous to flat adsorption and the formation of feedback bonds. This provided a molecular structural basis for the excellent corrosion inhibition properties of 2 N6O‐BT. [ABSTRACT FROM AUTHOR]

A significant focus of carbon dot research is on enhancing the fluorescence emission performance of biomimetic carbon dots to improve their application value in practical analysis. In this study, fish scales were used as a precursor, and citric acid was introduced to improve the quantum yield of carbon dots. The results showed that under 350 nm excitation, citric acid-modified carbon dots (CDs-FS/CA) exhibited a maximum fluorescence emission of 411 nm, and the emission behavior was independent of the excitation wavelength, with a quantum yield of 35.5%. This high quantum yield could be attributed to the presence of citric acid and the participation of hydroxyapatite in fish scales. The CDs-FS/CA had a moderate degree of graphitization, smaller and more concentrated particle size distribution, and a high proportion of pyrrole N. They showed good fluorescence performance through the synergistic effect of surface state sp2 C and different N-doped surface states. A good linear relationship in the range of 0–50 μmol L−1 was obtained using CDs-FS/CA for trace detection of quercetin, with a limit of detection of 3.8 nmol L−1, and good recovery in actual sample detection. These results offer a reference for enhancing the quantum yield of CDs obtained from alternative biomass sources and indicate the encouraging commercial feasibility of CDs derived from waste biomass for detecting trace amounts of quercetin. [ABSTRACT FROM AUTHOR]

The recent high demand of secondary electron emission yield (SEY) measurements in dielectric materials from space industry has driven SEY laboratories to improve their facilities and measurement techniques. SEY determination by the common capacitive method, also known as pulsed method, is well accepted and has given satisfactory results in most cases. Nevertheless, the samples under study must be prepared according to the experimental limitations of the technique, i.e. they should be manufactured separated from the devices representing faithfully the surface state of the own device and be as thin as possible. A method based on the Kelvin probe (KP) is proposed here to obtain the SEY characteristics of electrically floating Platinum, Kapton and Teflon placed over dielectric spacers with thicknesses ranging from 1.6 to 12.1 mm. The results are compared with those of the capacitive method and indicate that KP SEY curves are less sensitive to spacer thickness. An explanation based on the literature is also given. In all, we have established that KP is better suited for the analysis of dielectric samples thicker than 3 mm. [ABSTRACT FROM AUTHOR]

Optimization regarding the electronic structure of nanometal cocatalysts via alloying is considered as a promising strategy to regulate the formation of reactive oxygen species (ROS) in photocatalytic degradation. Herein, a series of g-C3N4-supported PdCu alloy cocatalysts were constructed to investigate the regulatory effect and mechanism of alloying on photocatalytic active species. Photocatalytic degradation experiments using ciprofloxacin (CIP) as a model pollutant demonstrated that optimal alloying with PdCu (Cu ≤ 0.5 wt %) significantly boosts the production of active species and incrementally enhances the contribution of superoxide anions (·O2–). The introduction of Cu leads to the redistribution of surface electrons in the PdCu alloy, resulting in a gradual strengthening of the O2 adsorption as the Cu content increases up to 0.5 wt %. The CIP degradation rate reaches a maximum of 80.5% at pH 6.7. Inorganic ions such as Na+ and Ca2+ inhibit degradation, while low concentrations of Fe3+ promote that. The CIP degradation rate in actual water samples ranges from 71.1 to 78.2%. Furthermore, the degradation pathway initiated from carbonyl destruction induced by a higher ·O2– concentration was proposed. This comprehensive study provides valuable insights into the design of alloyed photocatalysts, emphasizing the significance of optimizing metal composition to regulate ROS generation and enhance photocatalytic efficiency. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) are versatile, easy to fabricate, chemically stable, and ecofriendly materials. This work presents the impact of different post-treatments, such as centrifugation and filtration, on the photoluminescence (PL) and particle-size distribution of electrochemically synthesized CDs. Because organic envelope surfactants have been reported to influence PL, bare CDs were compared with CDs modified with amphiphilic and nonamphiphilic surfactants. The CD colloidal solution exhibited stabilization in the case of bare CDs and CDs modified with amphiphilic sodium dodecyl sulphate or non-amphiphilic surfactant sodium citrate, as indicated by the zeta potential. The experimental results also revealed a minor influence of the organic envelope on the absorbance or PL spectrum, whereas filtration of the colloid solution had a significant impact, revealing an effect not previously observed. The change in the absorbance spectrum was attributed to sp3 hybridization due to increased disorder and surface states during the filtration process. Absorbance deconvolution also disclosed two energy substates not mentioned elsewhere. The PL spectra of the filtered CD solutions revealed that the emission peaks shifted according to the incident wavelength, and the centrifuged CDs synthesized with the sodium citrate surfactant lacked PL due to the absence of sp3 states. This study emphasizes the importance of CD post-treatment in CD production rather than the use of surfactants. [ABSTRACT FROM AUTHOR]

Fit hypotheses are a common theme in psychological theories. Various theoretical approaches postulate that fit is also relevant for the within-person dynamics of personality states. A better understanding of these dynamics is important to comprehend the functioning of personality and its relations to relevant life outcomes. Two forms of fit are relevant for personality states: personality states that fit with characteristics of the current situation (state–situation fit) and personality states that fit with personality trait levels (state–trait fit). Both forms of fit are assumed to be related to more positive affect. In three intensive longitudinal studies (Sample 1: N = 194, 4,244 observations; Sample 2: N = 254, 7,667 observations; Sample 3: N = 374, 16,418 observations), we conducted moderated multilevel polynomial regression and response surface analysis to examine whether trait–state fit and state–situation fit were associated with state affect. Generally, there was no consistent evidence for state–trait fit, state–situation fit, or interactions between personality traits, personality states, and situation characteristics predicting momentary state affect. The analyses yielded several spurious significant fit and interaction effects that could however not be replicated in the other samples. Taken together, in one of the most comprehensive attempts to demonstrate fit effects in personality states to date, we could not find any consistent evidence for fit or interactions between personality traits, personality states, and situation characteristics predicting momentary affect. Furthermore, these findings emphasize the importance of replications and robustness checks when examining complex personality dynamics such as fit or interactions. [ABSTRACT FROM AUTHOR]

This paper provides a detailed description of the development and experimental results of the supercritical flow experiment payload carried on the TZ-6 cargo spacecraft, as well as a systematic verification of the out-of-cabin deployment experiment. The technical and engineering indicators of the payload deployment experiment are analyzed, and the functional modules of the payload are shown. The paper provides a detailed description of the design, installation location, size, weight, temperature, illumination, pressure, radiation, control, command reception, telemetry data, downlink data, and experimental procedures for the out-of-cabin payload in the extreme conditions of space. The paper presents the annular liquid surface state and temperature oscillation signals obtained from the space experiment and conducts ground matching experiments to verify the results, providing scientific references for the design and condition setting of space experiments and comparisons for the experimental results to obtain the flow field structure under supercritical conditions. The paper provides a specific summary and discussion of the space fluid science experiment project, providing useful references for future long-term in-orbit scientific research using cargo spacecraft. [ABSTRACT FROM AUTHOR]

To assess the contribution of residual stress to the improvement of high‐cycle fatigue (HCF) properties, HCF tests are performed on Ti‐6Al‐4V specimens with different residual stress levels but no other evident surface state modification induced by machining. Results indicate that compressive residual stress induced by machining significantly improves the HCF performance of Ti‐6Al‐4V specimens. Of all the specimens, the fatigue strength of specimens with a surface residual stress level of −400 MPa is increased by approximately 16.4%. Furthermore, to accurately predict the fatigue life based on three mean stress correction equations (e.g., Walker, Goodman, and Smith–Watson–Topper), the method of reducing surface residual stress by a reduction factor and then adding to the mean stress is proposed. A reduction factor of 0.55 is found to be appropriate for the alloy under the test condition, with majority of the predicted data falling within a factor of three scatter band. Highlights: Isolate residual stress from other surface integrity parameters by machining.Compressive residual stress improves both the fatigue life and strength.Effect of residual stress is considered by introducing a reduction factor in mean stress.Develop a life prediction method based on mean stress correction model. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) offer tremendous advantages in the fields such as bioimaging, sensing, biomedicine, catalysis, information encryption, and optoelectronics. However, the inherent challenge is synthesizing CDs with a full-spectrum emission, as most CDs typically produce only blue or green emissions, which severely hinder further investigation into their fluorescence mechanism and restrict their broader applications in light-emitting diodes (LEDs). In this work, we reported a solvent-controlled strategy for the preparation of multicolor CDs with blue, yellow, and red emissions, using o-phenylenediamine (oPD) and ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) as precursors. The detailed characterizations proved that a solvent with a lower boiling point and lower solubility of precursors resulted in a higher degree of dehydration and carbonization process, thereby increasing carbon cores with sp2-conjugated domains and nitrogen doping and further reducing the bandgap energies, causing a significant redshift emission from blue to red. The underlying fluorescence mechanism of the prepared multicolor CDs was contributed to the surface state. Eventually, blue-, yellow-, and red-emitting CDs based on poly(vinyl alcohol) (PVA) films and colorful LEDs devices were fabricated by dispersing the as-synthesized CDs into a PVA solution. The proposed solvent-controlled strategy for multicolor CDs preparation will be helpful for fully utilizing the advantages of CDs and expanding their applications. [ABSTRACT FROM AUTHOR]

Polarization, as a fundamental property of light, plays a key role in many phenomena of near‐field coupling, namely the coupling of source's evanescent waves into some guided modes. As a typical example of the polarization‐locked phenomenon in the near‐field coupling, the Janus dipole has the orientation of its near‐field coupling face intrinsically determined by the polarization state of linearly‐polarized surface waves, specifically whether they are transverse‐magnetic (TM) or transverse‐electric (TE) surface waves. Here, a mechanism to achieve the directional near‐field coupling of Janus dipoles beyond polarization locking by leveraging hybrid TM‐TE surface waves is presented. These hybrid surface waves, as eigenmodes with both TM and TE wave components, can be supported by optical interfaces between different filling materials inside a parallel‐plate waveguide. Under the excitation of hybrid surface waves, it is found that the coupling and non‐coupling face of a Janus dipole may be switched, if the Janus dipole itself rotates in a plane parallel to the designed optical interface between different filling materials, without resorting to the change of surface‐wave polarization. The underlying mechanism is due to the capability of hybrid surface waves to extract both the source's TM and TE evanescent waves, which offers an alternative paradigm to regulate the interference in the near‐field coupling. [ABSTRACT FROM AUTHOR]

The emerging field of topological catalysis has received significant attention due to its potential for high‐performance catalytic activity in the hydrogen‐evolution reaction (HER). While topological materials often possess fragile surface states, trivial topological materials not only offer a larger pool of candidates but also demonstrate robust surface states. As a result, the search for topological catalysts has expanded to include trivial schemes. In this study, a novel 2D Janus monolayer, MoSMg, which demonstrates exceptional obstructed atomic insulating behavior, is presented. Crucially, this trivial metallic topological state exhibits clean obstructed surface states, leading to a significant enhancement in catalytic performance for the HER in electrochemical processes, particularly under high hydrogen coverage. Moreover, the edge sites of this MoSMg monolayer exhibit even more superior catalytic activity, characterized by near‐zero Gibbs free energies. In these findings, the way is paved for exploring new avenues in the design of quantum electrocatalysts, especially within the realm of trivial topological materials. [ABSTRACT FROM AUTHOR]

Warp sizing significantly influences both the efficiency of weaving machines and the overall quality of the woven fabric, playing a crucial role in the weaving preparation process. Ensuring precise control of process parameters and equipment status during the sizing process is essential to maintain desirable sizing quality. This paper clarified the research significance of squeezing from the perspective of its application in warp sizing. Moreover, research advances in the squeezing device, including the structure, material, surface state of squeezing and sizing rollers, the configuration of the squeeze and sizing rollers, the spraying device, the pressurization methods for the squeezing roller, and their influence on sizing performance were reviewed in detail. A comprehensive analysis and summary were conducted to explore the correlations between sizing quality and diverse squeezing technical parameters, encompassing squeezing force, surface hardness of rubber-covered sizing and the squeezing roller, squeezing width, warp speed, and immersion time. In addition, this article also outlines the mathematical models related to the squeezing process and the characterization methods of the squeezing effect. Finally, it offers a glimpse into potential future research directions concerning the squeezing process. [ABSTRACT FROM AUTHOR]

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nuclear Safety is the property of Nuclear & Radiation Safety Center and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)