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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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Quantum spin systems: Toroidal classification and geometric duality

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Physical Review B 2024年第14期110卷 L140403页

作者： Vahid Azimi-Mousolou Anders Bergman Anna Delin Olle Eriksson Manuel Pereiro Danny Thonig Erik Sjöqvist Department of Applied Mathematics and Computer Science Faculty of Mathematics and Statistics Department of Physics and Astronomy Department of Applied Physics School of Engineering Sciences (SeRC) Wallenberg Initiative Materials Science for Sustainability (WISE) Wallenberg Initiative Materials Science WISE School of Science and Technology

We demonstrate a toroidal classification for quantum spin systems, revealing an intrinsic geometric duality within this structure. Through our classification and duality, we reveal that various bipartite quantum features in magnon systems can manifest equivalently in both bipartite ferromagnetic and antiferromagnetic materials, based upon the availability of relevant Hamiltonian parameters. Additionally, the results highlight the antiferromagnetic regime as an ultrafast dual counterpart to the ferromagnetic regime, both exhibiting identical capabilities for quantum spintronics and technological applications. Concrete illustrations are provided, demonstrating how splitting and squeezing types of two-mode magnon quantum correlations can be realized across ferro- and antiferromagnetic regimes.

关键词： Magnons Quantum correlations in quantum information Quantum information processing Quantum information theory Spintronics

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Point process microstructural model of metallic thin films with implications for coarsening

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npj Computational Materials 2023年第1期9卷 2074-2082页

作者： J.M.Rickman K.Barmak Y.Epshteyn C.Liu Department of Materials Science and Engineering Lehigh UniversityBethlehemPA 18015USA Department of Physics Lehigh UniversityBethlehemPA 18015USA Department of Applied Physics and Applied Mathematics Columbia UniversityNew YorkNY 10027USA Department of Mathematics The University of UtahSalt Lake CityUT 84112USA Department of Applied Mathematics Illinois Institute of TechnologyChicagoIL 60616USA

We develop a thin-film microstructural model that represents structural markers(i.e.,triple junctions in the two-dimensional projections of the structure of films with columnar grains)in terms of a stochastic,marked point process and the microstructure itself in terms of a grain-boundary *** advantage of this representation is that it is conveniently applicable to the characterization of microstructures obtained from crystal orientation mapping,leading to a picture of an ensemble of interacting triple junctions,while providing results that inform grain-growth models with experimental *** specifically,calculated quantities such as pair,partial pair and mark correlation functions,along with the microstructural mutual information(entropy),highlight effective triple junction interactions that dictate microstructural *** validate this approach,we characterize microstructures from Al thin films via crystal orientation mapping and formulate an approach,akin to classical density functional theory,to describe grain growth that embodies triple-junction interactions.

关键词： grain microstructure process

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Towards end-to-end structure determination from x-ray diffraction data using deep learning

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npj Computational Materials 2024年第1期10卷 1048-1059页

作者： Gabe Guo Judah Goldfeder Ling Lan Aniv Ray Albert Hanming Yang Boyuan Chen Simon J.L.Billinge Hod Lipson Department of Computer Science Columbia UniversityNew YorkNY10027USA Department of Applied Physics and Applied Mathematics Columbia UniversityNew YorkNY10027USA Department of Mechanical Engineering and Materials Science Duke UniversityDurhamNC27708USA Department of Mechanical Engineering Columbia UniversityNew YorkNY10027USA

Powder crystallography is the experimental science of determining the structure of molecules provided in crystalline-powder form,by analyzing their x-ray diffraction(XRD)*** many materials are readily available as crystalline powder,powder crystallography is of growing usefulness to many ***,powder crystallography does not have an analytically known solution,and therefore the structural inference typically involves a laborious process of iterative design,structural refinement,and domain knowledge of skilled experts.A key obstacle to fully automating the inference process computationally has been formulating the problem in an end-to-end quantitative form that is suitable for machine learning,while capturing the ambiguities around molecule orientation,symmetries,and reconstruction *** we present an ML approach for structure determination from powder diffraction *** works by estimating the electron density in a unit cell using a variational coordinate-based deep neural *** demonstrate the approach on computed powder x-ray diffraction(PXRD),along with partial chemical composition information,as *** evaluated on theoretically simulated data for the cubic and trigonal crystal systems,the system achieves up to 93.4%average similarity(as measured by structural similarity index)with the ground truth on unseen materials,both with known and partially-known chemical composition information,showing great promise for successful structure solution even from degraded and incomplete input *** approach does not presuppose a crystalline structure and the approach are readily extended to other situations such as nanomaterials and textured samples,paving the way to reconstruction of yet unresolved nanostructures.

关键词： structure powder crystalline

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Stretched non-negative matrix factorization

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npj Computational Materials 2024年第1期10卷 1248-1262页

作者： Ran Gu Yevgeny Rakita Ling Lan Zach Thatcher Gabrielle E.Kamm Daniel O’Nolan Brennan Mcbride Allison Wustrow James R.Neilson Karena W.Chapman Qiang Du Simon J.L.Billinge NITFID School of Statistics and Data ScienceNankai UniversityTianjinChina Department of Applied Physics and Applied Mathematics Fu Foundation School of Engineering&Applied SciencesColumbia UniversityNew YorkNYUSA Department of Chemistry Stony Brook UniversityStony BrookNYUSA Department of Chemistry Colorado State UniversityFort CollinsCOUSA

A novel algorithm,STRETCHEDNMF,is introduced for non-negative matrix factorization(NMF),accounting for signal stretching along the independent variable’s *** addresses signal variability caused by stretching,proving beneficial for analyzing data such as powder diffraction at varying *** approach provides a more meaningful decomposition,particularly when the component signals resemble those from chemical components in the *** STRETCHEDNMF model introduces a stretching factor to accommodate signal expansion,solved using discretization and Block Coordinate Descent *** experimental results indicate that the STRETCHEDNMF model outperforms conventional NMF for datasets exhibiting such *** enhanced version,SPARSE-STRETCHEDNMF,optimized for powder diffraction data from crystalline materials,leverages signal sparsity for accurate extraction,especially with small *** results showcase its effectiveness in analyzing diffraction data,including success in real-time chemical reaction experiments.

关键词： signal stretching matrix

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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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Active learning of ternary alloy structures and energies

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npj Computational Materials 2024年第1期10卷 2049-2059页

作者： Gaurav Deshmukh Noah J.Wichrowski Nikolaos Evangelou Pushkar G.Ghanekar Siddharth Deshpande Ioannis G.Kevrekidis Jeffrey Greeley Davidson School of Chemical Engineering Purdue UniversityWest LafayetteIN 47907USA Department of Applied Mathematics and Statistics Johns Hopkins UniversityBaltimoreMD 21218USA Department of Chemical and Biomolecular Engineering Johns Hopkins UniversityBaltimoreMD 21218USA

Machine learning models with uncertainty quantification have recently emerged as attractive tools to accelerate the navigation of catalyst design spaces in a data-efficient ***,we combine active learning with a dropout graph convolutional network(dGCN)as a surrogate model to explore the complex materials space of high-entropy alloys(HEAs).We train the dGCN on the formation energies of disordered binary alloy structures in the Pd-Pt-Sn ternary alloy system and improve predictions on ternary structures by performing reduced optimization of the formation free energy,the target property that determines HEA stability,over ensembles of ternary structures constructed based on two coordinate systems:(a)a physics-informed ternary composition space,and(b)data-driven coordinates discovered by the Diffusion Maps manifold learning *** reduced optimization techniques improve predictions of the formation free energy in the ternary alloy space with a significantly reduced number of DFT calculations compared to a high-fidelity *** physicsbased scheme converges to the target property in a manner akin to a depth-first strategy,whereas the data-driven scheme appearsmore akin to a breadth-first *** sampling schemes,coupled with our acquisition function,successfully exploit a database of DFT-calculated binary alloy structures and energies,augmented with a relatively small number of ternary alloy calculations,to identify stable ternary HEA compositions and *** generalized framework can be extended to incorporate more complex bulk and surface structural motifs,and the results demonstrate that significant dimensionality reduction is possible in thermodynamic sampling problems when suitable active learning schemes are employed.

关键词： alloy ternary structures

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Insights into adsorbent tortuosity across aqueous adsorption systems

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Particuology 2024年第5期88卷 71-88页

作者： Ackmez Mudhoo Marta Otero Khim Hoong Chu Department of Chemical and Environmental Engineering Faculty of EngineeringUniversity of MauritiusRéduit 80837Mauritius Department of Applied Chemistry and Physics Universidad de LeónCampus de Vegazana 24071 LeónSpain Department of Chemical Engineering Faculty of EngineeringUniversity of MalayaKuala Lumpur 50603Malaysia

Pore network,pore connectivity,and the resulting effective adsorbate pore diffusivity within an adsorbent are critical physical considerations in mass transport modeling of aqueous *** to these three adsorbent features are the adsorbent tortuosity and tortuosity factor *** concepts encompass the collective hindrance to intra-adsorbent adsorbate transport arising because of a disorderly adsorbent porous *** is crucial for materials scientists,chemists,chemical engineers,and water treatment specialists to understand the complex and variable connections among adsorbate chemistry,adsorbent chemistry,adsorbent porosity,pore shape,size,and tortuosity,pore wall effect,adsorbate-adsorbent interactions,and adsorbate-adsorbate interactions in competitively contaminated aqueous *** tortuosity has been sporadically studied in aqueous adsorption *** the small population of these studies,insightful observations and inferences have been ***,as it appears,no review has been published to compile,compare,and contrast these ***,this review concisely brings up those observations and interpretations around adsorbent tortuosity for aqueous adsorption *** notion of an adsorbent's tortuosity being single-valued is argued to be ***,perspectives are aired on possible research and development directions for elucidating the dynamic attributes of adsorbent tortuosity and applying them in real-scale adsorption-oriented water *** data acquired by filling in these research gaps can enable the design of adsorbents more adapted for real-scale water purification.

关键词： Adsorbent Tortuosity Porosity Pore diffusion models Aqueous systems

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Machine learning potential assisted exploration of complex defect potential energy surfaces

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npj Computational Materials 2024年第1期10卷 3017-3023页

作者： Chao Jiang Chris A.Marianetti Marat Khafizov David H.Hurley Computational Mechanics and Materials Department Idaho National LaboratoryIdaho FallsID 83415USA Department of Applied Physics and Applied Mathematics Columbia UniversityNew YorkNY 10027USA Department of Mechanical and Aerospace Engineering The Ohio State UniversityColumbusOH 43210USA Materials Science and Engineering Department Idaho National LaboratoryIdaho FallsID 83415USA

Atomic-scale defects generated in materials under both equilibrium and irradiation conditions can significantly impact their physical and mechanical *** the energetically most favorable ground-state configurations of these defects is an important step towards the fundamental understanding of their influence on the performance of materials ranging from photovoltaics to advanced nuclear ***,using fluorite-structured thorium dioxide(ThO_(2))as an exemplar,we demonstrate how density functional theory and machine learning interatomic potential can be synergistically combined into a powerful tool that enables exhaustive exploration of the large configuration spaces of small point defect *** study leads to several unexpected discoveries,including defect polymorphism and ground-state structures that defy our physical *** physical origins of these unexpected findings are elucidated using a local cluster expansion model developed in this work.

关键词： properties defect potential

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Laboratorial radiative shocks with multiple parameters and first quantifying verifications to core-collapse supernovae

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Science Bulletin 2024年第20期69卷 3188-3191页

作者： Lu Zhang Jianhua Zheng Zhenghua Yang Tianming Song Shuai Zhang Tong Liu Yunfeng Wei Longyu Kuang Longfei Jing Zhiwei Lin Liling Li Hang Li Jinhua Zheng Pin Yang Yuxue Zhang Zhiyu Zhang Yang Zhao Zhibing He Ping Li Dong Yang Jiamin Yang Zongqing Zhao Yongkun Ding Research Center of Laser Fusion China Academy of Engineering PhysicsMianyang 621900China Department of Astronomy Xiamen UniversityXiamen 361005China Institute of Applied Physics and Computational Mathematics Beijing 100088China

A radiative shock(RS)is one in which the density and temperature structures are affected by radiation from the shock-heated *** plays a special role in astrophysics as it nontrivially combines both hydrodynamics and radiation *** most astrophysical shocks,the temperature and density conditions lead to strong emission,with radiation thus playing a major role therein.

关键词： shocks radiative shock

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