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Hyperuniformity of maximally random jammed packings of hyperspheres across spatial dimensions

Physical Review E 2023年第6期108卷 064602-064602页

作者： Charles Emmett Maher Yang Jiao Salvatore Torquato Department of Chemistry Princeton University Princeton New Jersey 08544 USA Materials Science and Engineering Arizona State University Tempe Arizona 85287 USA Department of Physics Arizona State University Tempe Arizona 85287 USA Department of Physics Princeton University Princeton New Jersey 08544 USA Princeton Materials Institute Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA

The maximally random jammed (MRJ) state is the most random (i.e., disordered) configuration of strictly jammed (mechanically rigid) nonoverlapping objects. MRJ packings are hyperuniform, meaning their long-wavelength density fluctuations are anomalously suppressed compared to typical disordered systems, i.e., their structure factors S(k) tend to zero as the wave number |k| tends to zero. Here we show that generating high-quality strictly jammed states for Euclidean space dimensions d=3,4, and 5 is of paramount importance in ensuring hyperuniformity and extracting precise values of the hyperuniformity exponent α>0 for MRJ states, defined by the power-law behavior of S(k)∼|k|α in the limit |k|→0. Moreover, we show that for fixed d it is more difficult to ensure jamming as the particle number N increases, which results in packings that are nonhyperuniform. Free-volume theory arguments suggest that the ideal MRJ state does not contain rattlers, which act as defects in numerically generated packings. As d increases, we find that the fraction of rattlers decreases substantially. Our analysis of the largest truly jammed packings suggests that the ideal MRJ packings for all dimensions d≥3 are hyperuniform with α=d−2, implying the packings become more hyperuniform as d increases. The differences in α between MRJ packings and the recently proposed Manna-class random close packed (RCP) states, which were reported to have α=0.25 in d=3 and be nonhyperuniform (α=0) for d=4 and d=5, demonstrate the vivid distinctions between the large-scale structure of RCP and MRJ states in these dimensions. Our paper clarifies the importance of the link between true jamming and hyperuniformity and motivates the development of an algorithm to produce rattler-free three-dimensional MRJ packings.

关键词： Granular solids

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Thermodynamic modeling of the LiCl-KCl-LaCl3 system with Bayesian model selection and uncertainty quantification

arXiv

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arXiv 2024年

作者： Gong, Rushi Shang, Shun-Li Goncharov, Vitaliy G. Cockrell, Cillian Trachenko, Kostya Bingham, Paul A. Guo, Xiaofeng Liu, Zi-Kui Department of Materials Science and Engineering The Pennsylvania State University University ParkPA16802 United States Department of Chemistry Washington State University PullmanWA99164 United States Materials Science and Engineering Program Washington State University PullmanWA99164 United States Nuclear Futures Institute Bangor University BangorLL57 1UT United Kingdom School of Physical and Chemical Sciences Queen Mary University of London Mile End Road LondonE1 4NS United Kingdom Materials and Engineering Research Institute Sheffield Hallam University SheffieldS1 1WB United Kingdom

Chloride molten salts are increasingly used in pyroprocessing techniques for the separation of lanthanides. Understanding thermodynamic properties of these salts is essential to predict their critical characteristics and optimize the separation process. Several thermodynamic models, including the associate model, the two-sublattice ionic model, and the modified quasichemical model with quadruplet approximation (MQMQA), have been utilized in the literature to capture the complexity of molten salts. In the present work, the Bayes factor is used to guide the model selection process for thermodynamic modeling of the KCl-LaCl3 system and provide statistical comparison of various models. The results indicate that the MQMQA model is the most favorable one based on available data. The LiCl-KCl-LaCl3 system has been further modelled with uncertainty quantification (UQ) using MQMQA with the thermodynamic properties of compounds in KCl-LaCl3 predicted by the quasiharmonic approach in terms of first-principles phonon calculations as a function of temperature. The calculated phase stability shows excellent agreement with experimental data, indicating that an appropriate thermodynamic model is important for accurately predicting critical characteristics of complex molten salts. © 2024, CC BY-NC-SA.

关键词： Lithium Chloride

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Structural changes induced by electric currents in a single crystal of Pr2CuO4

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Physical Review materials 2023年第8期7卷 083803-083803页

作者： Susmita Roy Feng Ye Zachary Morgan Kabir Mathur Anish Parulekar Syed I. A. Jalali Yu Zhang Gang Cao Nobu-Hisa Kaneko Martin Greven Rishi Raj Dmitry Reznik Department of Physics University of Colorado at Boulder Boulder Colorado 80309 USA Neutron Scattering Division Oak Ridge National Laboratory Oak Ridge Tennessee 37830 USA Materials Science and Engineering Program Department of Mechanical Engineering University of Colorado Boulder Boulder Colorado 80309 USA National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba Ibaraki 305-8563 Japan School of Physics and Astronomy University of Minnesota Minneapolis Minnesota 55455 USA Center for Experiments on Quantum Materials University of Colorado at Boulder Boulder Colorado 80309 USA

We demonstrate an approach to the structural and electronic property modification of perovskites, focusing on Pr2CuO4, an undoped parent compound of a class of electron-doped copper-oxide superconductors. Currents were passed parallel or perpendicular to the copper oxygen layers with the voltage ramped up until a rapid drop in the resistivity was achieved, a process referred to as “flash.” The current was then further increased tenfold in current-control mode. This state was quenched by immersion into liquid nitrogen. Flash can drive many compounds into different atomic structures with new properties, whereas the quench freezes them into a long-lived state. Single-crystal neutron diffraction of as-grown and modified Pr2CuO4 revealed a 10×10 superlattice due to oxygen-vacancy order. The diffraction peak intensities of the superlattice of the modified sample were significantly enhanced relative to the pristine sample. Raman-active phonons in the modified sample were considerably sharper. Measurements of electrical resistivity, magnetization, and two-magnon Raman scattering indicate that the modification affected only the Pr-O layers, but not the Cu-O planes. These results point to enhanced oxygen-vacancy order in the modified samples well beyond what can be achieved without passing electrical current. Our work opens a new avenue toward electric field/quench control of structure and properties of layered perovskite oxides.

关键词： Electrical properties Electroluminescence Magnetic order Magnetic susceptibility Superconductivity

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Noncured graphene thermal interface materials: Minimizing the thermal contact resistance

arXiv

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arXiv 2021年

作者： Sudhindra, Sriharsha Kargar, Fariborz Balandin, Alexander A. Center Department of Electrical and Computer Engineering Materials Science and Engineering Program University of California RiversideCA92521 United States

We report on experimental investigation of thermal contact resistance, Rc, of the noncuring graphene thermal interface materials with the surfaces characterized by different degree of roughness, Rc. It is found that the thermal contact resistance depends on the graphene loading, N, non-monotonically, achieving its minimum at the loading fraction of N 15 Rc.%. Increasing the surface roughness by Sq~1 μm results in approximately the factor of ×2 increase in the thermal contact resistance for this graphene loading. The obtained dependences of the thermal conductivity, KTIM, thermal contact resistance, Rc, and the total thermal resistance of the thermal interface material layer on and Rc indicate the need for optimization of the loading fraction of graphene for specific materials and roughness of the connecting surfaces. Our results are important for the thermal management of high-power-density electronics. Copyright © 2021, The Authors. All rights reserved.

关键词： Surface roughness

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Manipulating Fano coupling in an opto-thermoelectric field

arXiv

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arXiv 2024年

作者： Lin, Linhan Lepeshov, Sergey Krasnok, Alex Huang, Yu Jiang, Taizhi Peng, Xiaolei Korgel, Brian A. Alu, Andrea Zheng, Yuebing State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision Instrument Tsinghua University Beijing100084 China Department of Electrical and Photonics Engineering DTU Electro Technical University of Denmark Building 343 Kgs. LyngbyDK-2800 Denmark Department of Electrical and Computer Engineering Florida International University MiamiFL33174 United States School of Physics and Electronics Hunan University Changsha410082 China Mc Ketta Department of Chemical Engineering The University of Texas at Austin AustinTX78712 United States Materials Science & Engineering Program Texas Materials Institute The University of Texas at Austin AustinTX78712 United States Department of Electrical and Computer Engineering The University of Texas at Austin AustinTX78712 United States Advanced Science Research Center City University of New York New YorkNY10031 United States Physics Program Graduate Center City University of New York NY10016 United States Walker Department of Mechanical Engineering The University of Texas at Austin AustinTX78712 United States

Fano resonances in photonics arise from the coupling and interference between two resonant modes in structures with broken symmetry. They feature an uneven and narrow and tunable lineshape, and are ideally suited for optical spectroscopy. Many Fano resonance structures have been suggested in nanophotonics over the last ten years, but reconfigurability and tailored design remain challenging. Herein, we propose an all-optical "pick-and-place" approach aimed at assemble Fano metamolecules of various geometries and compositions in a reconfigurable manner. We study their coupling behavior by in-situ dark-field scattering spectroscopy. Driven by a light-directed opto-thermoelectric field, silicon nanoparticles with high quality-factor Mie resonances (discrete states) and low-loss BaTiO3 nanoparticles (continuum states) are assembled into all-dielectric heterodimers, where distinct Fano resonances are observed. The Fano parameter can be adjusted by changing the resonant frequency of the discrete states or the light polarization. We also show tunable coupling strength and multiple Fano resonances by altering the number of continuum states and discrete states in dielectric heterooligomers. Our work offers a general design rule for Fano resonance and an all-optical platform for controlling Fano coupling on demand. Copyright © 2024, The Authors. All rights reserved.

关键词： Light polarization

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Ronchigram Simulation and Training through ***

arXiv

引用

arXiv 2022年

作者： Sung, Suk Hyun Schnitzer, Noah Millsaps, William Kourkoutis, Lena F. Hovden, Robert Department of Materials Science and Engineering University of Michigan Ann ArborMI48109 United States Department of Materials Science and Engineering Cornell University IthacaNY14853 United States Engineering Physics Program University of Michigan Ann ArborMI48109 United States School of Applied and Engineering Physics Cornell University IthacaNY14853 United States Kavli Institute Cornell for Nanoscale Science Cornell University IthacaNY14853 United States

This article introduces a training simulator for electron beam alignment using Ronchigrams. The interactive web application, ***, is an advanced educational tool aimed at making scanning transmission electron microscopy (STEM) more accessible and open. For experienced microscopists, the tool offers on-hand quantification of simulated Ronchigrams and their resolution limits. © 2022, CC BY.

关键词： High resolution transmission electron microscopy

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Stress-tailoring magnetic anisotropy of V2O3/Ni bilayers

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Physical Review materials 2022年第6期6卷 064408-064408页

作者： Christian T. Wolowiec Juan Gabriel Ramírez Min-Han Lee Nareg Ghazikhanian Nicolas M. Vargas Ali C. Basaran Pavel Salev Ivan K. Schuller Department of Physics University of California San Diego La Jolla California 92093 USA Department of Physics Universidad de los Andes Bogotá 111711 Colombia Materials Science and Engineering Program University of California San Diego La Jolla California 92093 USA

We report on a temperature-driven reversible change of the in-plane magnetic anisotropy of V2O3/Ni bilayers. This is caused by the rhombohedral to monoclinic structural phase transition of V2O3 at TC=160 K. The in-plane magnetic anisotropy is uniaxial above TC, but as the bilayer is cooled through the structural phase transition, a secondary magnetic easy axis emerges. Ferromagnetic resonance measurements show that this change in magnetic anisotropy is reversible with temperature. We identify two structural properties of the V2O3/Ni bilayers affecting the in-plane magnetic anisotropy: (1) a growth-induced uniaxial magnetic anisotropy associated with steplike terraces in the bilayer microstructure and (2) a low-temperature strain-induced biaxial anisotropy associated with the V2O3 structural phase transition. Magnetoresistance measurements corroborate the change in magnetic anisotropy across the structural transition and suggest that the negative magnetostriction of Ni leads to the emergence of a strain-induced easy axis. This shows that a temperature-dependent structural transition in V2O3 may be used to tune the magnetic anisotropy in an adjacent ferromagnetic thin film.

关键词： Anisotropic magnetoresistance Magnetic anisotropy Magnetization switching Magnetoresistance Magnetostriction Magnetotransport Microstructure Strain Structural phase transition Bilayer films Functional materials Magnetic systems Thin films Ferromagnetic resonance Microwave techniques Resistivity measurements X-ray diffraction

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Effect of surface steps on chemical ordering in the subsurface of Cu(Au) solid solutions

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Physical Review B 2021年第3期103卷 035401-035401页

作者： Kuo Liu Siming Zhang Dongxiang Wu Langli Luo Xianhu Sun Xiaobo Chen Dmitri Zakharov Shaobo Cheng Yimei Zhu Judith C. Yang Guofeng Wang Guangwen Zhou Department of Mechanical Engineering and Materials Science and Engineering Program State University of New York Binghamton New York 13902 USA Department of Mechanical Engineering and Materials Science University of Pittsburgh Pittsburgh Pennsylvania 15261 USA Center for Functional Nanomaterials Brookhaven National Laboratory Upton New York 11973 USA Department of Condensed Matter Physics and Materials Science Brookhaven National Laboratory Upton New York 11973 USA Department of Chemical and Petroleum Engineering University of Pittsburgh Pittsburgh Pennsylvania 15261 USA

Atomic steps are typically assumed to only influence surface phenomena of solids. In contrast, here we show, using in situ atomic-resolution electron microscopy observations and atomistic modeling, the pronounced effect from surface steps in inducing compositional and structural evolution in the subsurface of a Cu(Au) solid solution. We find that Au surface segregation results in a stacked sequence of Cu-Au ordered phases in the subsurface. The presence of a monatomic step at the surface induces the formation of an antiphase boundary that extends from the surface step to deeper layers by maintaining the same composition profile associated with each terrace. The bunching of surface steps induces chemical disordering of the Cu-Au ordered phases in the subsurface region of the bunched steps. These results demonstrate the instant propagation of surface dynamics of atomic steps into the subsurface region and can find broader applicability in utilizing surface defects to tune the composition and structure in the subsurface of alloys.

关键词： Structural properties Surface & interfacial phenomena Alloys Density functional theory Electron microscopy

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Advanced Under-Rails Fiber-Optic Sensor for Detection of Rolling Stock and Axles in Tram Transport

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IEEE Transactions on Instrumentation and Measurement 2025年 74卷

作者： Fajkus, Marcel Jargus, Jan Nedoma, Jan Kepak, Stanislav Krizan, Daniel Cubik, Jakub Krenzelok, Tomas Leal, Arnaldo Marques, Carlos VSB—Technical University of Ostrava Faculty of Electrical Engineering and Computer Science Department of Telecommunications Ostrava708 00 Czech Republic Prodin a.s. Pardubice530 02 Czech Republic Graduate Program in Electrical Engineering Federal University of Espirito Santo Vitoria29075-910 Brazil University of Aveiro CICECO—Aveiro Institute of Materials Physics Department Aveiro3810-193 Portugal VSB—Technical University of Ostrava Department of Physics Ostrava708 00 Czech Republic

This article describes the implementation of an advanced fiber-optic intensity sensor for the comprehensive detection of axles and bogies of rail vehicles in tram transport. The sensor uses the principle of optical fiber bending, where the intensity of transmitted light is modulated due to mechanical stress on the fiber caused by the passage of a tram and the subsequent reversible deformation of the rail. The innovative design of the sensor allows for its easy installation under the rail foot, between the rail and the sleeper, replacing conventional anti-vibration pads, and includes specially designed deformable elements which the optical fiber bends and modulates the transmitted light intensity. During long-term testing (11 months in various weather conditions) conducted in the real tram depot (Ostrava, Czech Republic), 20602 tram passages were secured and analyzed. The sensor demonstrated success in detecting bogies, achieving 100% accuracy with no false positives (FPs) or false negatives (FNs). Axle detection showed an average success rate of 86.1%, with variability among different tram types up to 97.8%. The signal modulation was also subjected to detailed analysis, revealing differences in responses between various tram types, which can be attributed to differences in bogie construction and vehicle weight. Due to its electromagnetic immunity, the implemented fiber-optic sensor offers the potential for more reliable detection and broad application possibilities, including track occupancy monitoring, speed measurement, or determining the direction of travel on single-track lines. With slight optimization, the sensor could also be used to weigh rail vehicles or as an axle counter in railway or light rail transport. © 1963-2012 IEEE.

关键词： Bogies (railroad rolling stock)

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Piezo-Flexocatalysis of Single-Atom Pt-Loaded Graphitic Carbon Nitride

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Small Methods 2024年第7期8卷 e2301287页

作者： Wang, Yu Teng Lin, Hsun-Yen Chen, Yu-Ching Lin, Yan-Gu Wu, Jyh Ming Department of Materials Science and Engineering National Tsing Hua University 101 Section 2 Kuang Fu Road Hsinchu300 Taiwan Program in Prospective Functional Materials Industry National Tsing Hua University 101 Section 2 Kuang Fu Road Hsinchu300 Taiwan National Synchrotron Radiation Research Center 101 Hsin-Ann Road Hsinchu Science Park Hsinchu300092 Taiwan High Entropy Materials Center National Tsing Hua University 101 Section 2 Kuang Fu Road Hsinchu300 Taiwan

This study develops a single-atom Pt-loaded graphitic carbon nitride (SA-Pt/CN) and evaluates its piezo-flexocatalytic properties by conducting a hydrogen evolution reaction (HER) and Rhodamine B (RB) dye degradation test under ultrasonic vibration in the dark. SA-Pt/CN has a hydrogen gas yield of 1283.8 µmol g−1 h−1, which is 23.3 times higher than that of pristine g-C3N4. Moreover, SA-Pt/CN enhances the dye degradation reaction rate by ≈2.3 times compared with the pristine sample. SA-Pt/CN exhibits lattice distortion and strain gradient enlargement caused by the single atom Pt at the N sites of g-C3N4, which disrupts the symmetric structure and contributes to the enhancement of piezoelectric and flexoelectric polarization. As far as it is known, this is the first study to investigate the piezo-flexocatalytic reaction of SA-Pt/CN without light irradiation and provides new insights into single-atom piezocatalysts. © 2023 Wiley-VCH GmbH.

关键词： Degradation

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