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Charge fluctuations in a cluster Mott state: Hard x-ray photoemission study on a breathing kagome magnet Nb3Cl8

Physical Review B 2024年第8期110卷 L081109-L081109页

作者： R. Nakamura D. Takegami K. Fujinuma M. Nakamura M. Ferreira-Carvalho A. Melendez-Sans M. Yoshimura K.-D. Tsuei Y. Haraguchi H. Aruga Katori L. H. Tjeng T. Mizokawa Department of Applied Physics 01187 Dresden Germany Institute of Physics II 30076 Hsinchu Taiwan Department of Applied Physics and Chemical Engineering

We report on our hard x-ray photoemission study of Nb3Cl8, wherein the breathing Kagome lattice of Nb provides interesting magnetic properties with spin 1/2 per Nb trimer. The Nb3d5/2 and 3d3/2 core level peaks are accompanied by satellite peaks, suggesting the importance of Nb4d charge degrees of freedom. The Cl1s and 2p core level spectra have high binding energy peaks which can be assigned to the Cl site with Cl3p ligand holes near the center of the Nb trimer. The core level spectra indicate that the Nb-Nb and Nb-Cl charge fluctuations play crucial roles in the magnetic interaction between the trimers.

关键词： Frustrated magnetism Kagome lattice Mott insulators Density functional theory Photoemission

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Emerging direct current triboelectric nanogenerator for high-entropy mechanical energy harvesting

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Science China(Technological Sciences) 2024年第5期67卷 1297-1316页

作者： CHEN Jie GUO RuiLong GUO HengYu College of Physics and Electronic Engineering Chongqing Normal UniversityChongqing 401331China Department of Applied Physics Chongqing UniversityChongqing 401331China

In the era of the Internet of Things(IoT),the provision of sustainable power to distributed,mobile,and low-power-consumption electronic devices is a critical *** overcome this challenge,the triboelectric nanogenerator(TENG),a highly efficient high-entropy mechanical energy harvesting device,was developed in *** device enables the direct conversion of irregular and low-frequency mechanical energy into pulsed alternating current(AC)***,the incompatibility of most electronic devices with AC signals necessitates rectifier circuits or generators that deliver direct current(DC)*** recent years,DC-TENGs have undergone extensive development,achieving significant milestones in various application fields while also facing crucial challenges that require *** this review,three categories of DC-TENG devices with distinct operating mechanisms are comprehensively explored:multiphase coupling,mechanical rectification,and air *** typical structures and working mechanisms are thoroughly discussed,and specific output performance limitations,along with corresponding optimization strategies,are ***,the applications of DC-TENGs in various scenarios are ***,the challenges faced by DC-TENGs and potential solutions are analyzed to guide further advancements in this technology.

关键词： TENG direct current working mechanisms output performance limitations optimization strategies

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Triple-function Mn regulation of NiFe(oxy)hydroxide for oxygen evolution reaction

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材料科学技术（英文版） 2025年第4期207卷 1-9页

作者： Hui Wan Meng-Yuan Xie Bo Li Jian-Hang Nie Tao Huang Lei Li Jing-Hui Shi Ming-Hua Xian Jia-Rong Huang Wangyu Hu Gui-Fang Huang Fei Gao Wei-Qing Huang Department of Applied Physics School of Physics and ElectronicsHunan UniversityChangsha 410082China School of Materials and Environmental Engineering Changsha UniversityChangsha 410082China Department of Applied Physics School of Physics and ElectronicsHunan UniversityChangsha 410082China College of Materials Science and Engineering Hunan UniversityChangsha 410082China Department of Nuclear Engineering and Radiological Sciences University of MichiganAnn ArborMI 48109USA

Transition metal(oxy)hydroxides are potential oxygen evolution reaction(OER)electrocatalysts;however,simultaneously modulating multiple factors to enhance their performance is a grand ***,we report an incorporating heteroatom strategy via one-step hydrothermal approach to adjust more than one factor of Mn-doped NiFe(oxy)hydroxide(Mn-NiFeOOH/LDH)*** doping regulates heterojunction morphology(reducing nanoparticles and becoming thinner and denser nanosheets),Ni/Fe ratio and valence states(Ni2+,Ni3+,and Ni3+Δ)of Ni *** former could effectively increase surface active sites,and the latter two reduce the content of Fe in the Mnx-NiFeOOH/LDH heterojunction,en-abling more Ni2+convert to Ni3+/3+Δ that have higher intrinsic OER *** a result,the first-rank Mn-NiFeOOH/LDH with ultra-low overpotential of 185 mV@20 mA cm-2 and 296 mV@500 mA cm-2,and the improved OER performance are outdo to those of commercial RuO2 catalyst for ***,the Mn-NiFeOOH/LDH affords the earliest initial potential(1.392 V ***),corresponds to a recorded low overpotential(162 mV).Based on the density functional theory(DFT),Mn dopants can alter intermedi-ate adsorption energy and effectively decrease·OOH's energy *** research exhibits a feasible strategy to design low cost electrocatalysts and provide new possibilities for future industrialization.

关键词： Electrocatalysts Triple-function Heteroatoms adjusting DFT Oxygen evolution reaction

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Moisture absorption behavior of epoxy-kenaf composites enhanced with surface-modified nano-clay

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Interactions 2025年第1期246卷 1-14页

作者： Ganvir, Vikrant Yashwant Ganvir, Hemlata Vikrant Department of Applied Physics Yeshwantrao Chavan College of Engineering Maharastra Nagpur India

Ultrasonication and magnetic stirring were used to disseminate surface-modified Bentonite nano-clay (2 wt%) into the epoxy Kenaf composite, which helped to reduce the problem of moisture absorption of Kenaf Fibers. A combination of compression molding and hand layup processes were employed to create epoxy nano-clay composites and Kenaf reinforced epoxy. The effect of surface modified nano-clay on artificial seawater absorption was studied by immersing the manufactured composite samples in artificial seawater till saturation. The uptake of moisture was calculated by taking regular weight readings and then calculating the diffusion coefficient. The saturation moisture uptake was reduced by 52% and the diffusion coefficient was reduced by 73% when nano-clay was added. It was determined how the tensile and flexural strengths were affected by the artificial absorption of seawater. Composites with epoxy nano-clay reinforcement and those with Kenaf reinforcement had a 27% decrease in tensile strength. The epoxy nano-clay composite showed no noticeable change, however the epoxy composite reinforced with Kenaf had a 19% reduction in tensile modulus. The flexural properties followed a comparable trend. Scanning electron micrographs (SEMs) show that nanoclay has mitigated the effect of water absorption on mechanical characteristics. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.

关键词： Compression molding

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A comparative study on optimizing chemical treatment parameters to enhance mechanical properties of sisal fiber-polycaprolactone composites

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Interactions 2024年第1期245卷 1-18页

作者： Ganvir, Hemlata Vikrant Ganvi, Vikrant Yashwant Department of Applied Physics Yeshwantrao Chavan College of Engineering Maharastra Nagpur India

Sisal fiber/polycaprolactone (SF/PCL) composites are a new and exciting development in the field of sustainable materials research. Enhancing the physical strength of these SF/PCL composites has been the primary emphasis of the present study work. The most efficient strategies to increase the chemical treatment process have been identified using methodologies such as Taguchi’s and Grey Relational Analysis (GRA). The injection molding technique was used to make the composites while important variables were changed. Chemical treatments solutions (potassium hydroxide, lithium hydroxide, and potassium acetate), chemical concentration (2%, 4%, and 6% w/v), and treatment duration (3, 6, and 9 h) were the variables for this work. Various SF/PCL composite variations were produced as a result of these adjustments. A number of physical properties were measured to assess the improved composites’ strength, including modulus of elasticity, flexural strength, impact resistance, deformability under bending, elongation under tension, and tensile strength. To examine the examined and treated materials in detail, we employed a scanning electron microscope (SEM). Using GRA and mean plots, the composite’s ideal values were the same. The optimal parameters for X1-Y2-Z2 were determined to enhance the mechanical properties of SF/PCL, which are KOH, 4%, and 4 h. However, the microstructure of the PCL matrix bio-composite strengthened with sisal fiber was affected by a variety of surface treatments. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.

关键词： Potassium hydroxide

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Indirect-to-direct band gap transition induced by d−d coupling between cations in rare-earth chalcogenide perovskites

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Physical Review B 2024年第4期110卷 L041201-L041201页

作者： Han Zhang Yichun Pan Zexin Liu Biao Zeng Xiaowei Wu Chen Ming Guoqing Xin Weihang Zhou Hao Zeng Shengbai Zhang Yi-Yang Sun State Key Laboratory of High Performance Ceramics and Superfine Microstructure Center of Materials Science and Optoelectronics Engineering Wuhan National High Magnetic Field Center and School of Physics Department of Physics University at Buffalo The Department of Physics Applied Physics and Astronomy

Chalcogenide perovskite materials have been shown to exhibit excellent properties for optoelectronics and photovoltaics. The research, however, has been focused on the II-IV-S3 series of compounds. Here, by theoretical calculation, we predict that in the III-III-S3 perovskites, there could exist a transition between the indirect and direct band gaps induced by the coupling strength of the d orbitals between the A-site and B-site cations. We validate this prediction by synthesizing LaScS3 through solid state reaction from three elemental materials. Micro-Raman analysis combined with Raman tensor calculations are used to identify the perovskite phase of micrometer-size grains, from which photoluminescence can be observed. The emitted light peaks at about 519 nm (or 2.39 eV), which corresponds to the largest band gap among the sulfide perovskites. The discovery of light-emitting LaScS3 enriches the family of chalcogenide perovskites for optoelectronic applications.

关键词： Band gap First-principles calculations Luminescence Optoelectronics Perovskites

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Deconfined quantum phase transition on the kagome lattice: Distinct velocities of spinon and string excitations

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Physical Review B 2024年第14期109卷 L140404-L140404页

作者： Dong-Xu Liu Zijian Xiong Yining Xu Xue-Feng Zhang (张学锋) Department of Physics Chongqing University Chongqing 401331 China Department of Applied Physics University of Tokyo Tokyo 113-8656 Japan College of Physics and Electronic Engineering Chongqing Normal University Chongqing 401331 China

A deconfined quantum phase transition (DQPT) provides an extraordinary possibility of the quantum phase transition beyond the Ginzburg-Landau paradigm, which is interwoven with numerous exotic phenomena of the strongly correlated quantum many-body system, e.g., fractional excitation, emergent symmetries, and gauge field. However, various candidates of DQPT have been demonstrated to be weakly first order, and the conformal field theory has to be altered into a nonunitary one. Here we numerically found two linear dispersions with different velocities in one of the few survivors of DQPT—the extended hard-core Bose-Hubbard model on the kagome lattice. Such counterintuitive results directly lead to the negation of possible emergent Lorentz symmetry and the breakdown of conventional theory of DQPT. Furthermore, the snapshots of boson configuration hint that these two velocities may correspond to the dynamics of the fractional excitations and quantum strings, respectively. Our work will inspire researchers to revisit the theory of DQPT and benefit the field of quantum materials and quantum simulations.

关键词： Critical phenomena Fractionalization Frustrated magnetism Geometric & topological phases Quantum field theory (low energy) Quantum phase transitions Quantum simulation Gauge symmetries Quantum Monte Carlo Symmetries

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Group IV topological quantum alloy and the role of short-range order:the case of Ge-rich Ge_(1–x)Pb_(x)

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npj Computational Materials 2024年第1期10卷 2397-2403页

作者： Yunfan Liang Shunda Chen Xiaochen Jin Damien West Shui-Qing Yu Tianshu Li Shengbai Zhang Department of Physics Applied Physicsand AstronomyRensselaer Polytechnic InstituteTroyNY 12180USA Department of Civil and Environmental Engineering George Washington UniversityWashingtonDC 20052USA Department of Electrical Engineering University of ArkansasFayettevilleAR 72701USA

Despite the explosion of interest in topological materials over the last decades,their applications remain limited due to challenges in growth and incorporation with today’s *** a potential bridge to close this gap,we investigate the group-IV alloy Ge_(1–x)Pb_(x),in the Ge-rich condition using density functional theory and show that relatively low concentrations of Pb(~9.4%)can lead to a topological phase transition.

关键词： alloy transition

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Optimizations and applications in large-scale scenes of Monte Carlo geometry conversion code CMGC

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Nuclear Science and Techniques 2025年第4期36卷 220-232页

作者： Xin Wang Ling-Yu Zhang Xue-Ming Shi Zhen Wu Jun-Li Li Gui-Ming Qin Yuan-Guang Fu CAEP Software Center for High Performance Numerical Simulation Beijing 100088China Institute of Applied Physics and Computational Mathematics Beijing 100088China Department of Engineering Physics Tsinghua UniversityBeijing 100084China

In response to the demand for rapid geometric modeling in Monte Carlo radiation transportation calculations for large-scale and complex geometric scenes,functional improvements,and algorithm optimizations were performed using CAD-to-Monte Carlo geometry conversion(CMGC)*** representation(BRep)to constructive solid geometry(CSG)conversion and visual CSG modeling were combined to address the problem of non-convertible geometries such as spline *** splitting surface assessment method in BRep-to-CSG conversion was optimized to reduce the number of Boolean operations using an Open ***,in turn,reduced the probability of CMGC conversion *** auxiliary surface generation algorithm was optimized to prevent the generation of redundant auxiliary surfaces that cause an excessive decomposition of CAD geometry *** optimizations enhanced the usability and stability of the CMGC model *** was applied successfully to the JMCT transportation calculations for the conceptual designs of five China Fusion engineering Test Reactor(CFETR)*** rapid replacement of different blanket schemes was achieved based on the baseline CFETR *** geometric solid number of blankets ranged from hundreds to tens of *** correctness of the converted CFETR models using CMGC was verified through comparisons with the MCNP calculation *** CMGC supported radiation field evaluations for a large urban scene and detailed ship *** enabled the rapid conversion of CAD models with thousands of geometric solids into Monte Carlo CSG *** analysis of the JMCT transportation simulation results further demonstrated the accuracy and effectiveness of the CMGC.

关键词： Monte Carlo CAD BRep to CSG CMGC

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Luminescence study of ZnS/PVK nanocomposites

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Materials Today: Proceedings 2023年 76卷 346-351页

作者： Nandini Nagwanshi, Durgesh Department of Applied Physics Jabalpur Engineering College MP Jabalpur India

Sulphide-based luminescence materials have attracted more curiosity for their extensive applications in electro and photoluminescence devices. One of the sulphides, such as zinc sulphide (ZnS), is a favourable material for phosphor growth in various bands for visible emission. The composition of the polymer matrix with ZnS demonstrates its special functions and stabilizes the nanoparticles. We have used chemical methods for the preparation of ZnS/PVK nanocomposites and reported their synthesis, photoluminescence (PL), and electroluminescence (EL) studies. The samples were analyzed through SEM (Scanning Electron Microscope), AFM (Atomic Force Microscope), and XRD (X-ray Diffraction). The XRD study shows the formation of ZnS nanocrystals with a cubic crystal structure, having a size between 3 and 12 nm and the broadening of peaks shows the formation of an amorphous compound. The AFM and SEM show clusters of particles in the range of a few tens to a few hundred nm. The results from all three studies show an increase in the size of particles with the ZnS loading in PVK (poly N-vinylcarbazole). The PL of a PVK sample excited at 400 nm shows a single PL peak at 451 nm and covers the spectral range from 400 to 600 nm. ZnS/PVK samples excited by 370 nm, give a PL peak due to PVK near 450 nm and when excited by 425 nm, the PL peak is found near 470 nm due to defect-related transitions in ZnS. In both cases, PL intensity increases with increasing ZnS loading in PVK. This may be because of interfacial charge transfer and radiative recombination. The EL studies show that corresponding to the applied voltage, the brightness is increased. The EL emission starts at a lower threshold voltage with a higher loading of ZnS in PVK and at a higher threshold voltage for higher frequencies. EL intensity of the composites increases with increasing ZnS loading in PVK. The voltage-current curve shows the linear relationship between voltage and current that is ohmic in nature. The frequency o

关键词： Zinc sulfide

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