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Intrinsic high-temperature ferroelectricity, superferroelasticity, and deep-ultraviolet nonlinear optical response of GaOCl monolayer

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Physical Review Materials 2024年第5期8卷 054003-054003页

作者： Zhenyuan Tu Yunhua Wang Weitu Liao Tao Hu Shengjun Yuan Shenzhen JL Computational Science and Applied Research Institute Shenzhen 518131 China Beijing 100193 China Lanzhou Center of Theoretical Physics & Key Laboratory for Quantum Theory and Applications of the Ministry of Education & Key Laboratory of Theoretical Physics of Gansu Province & School of Physical Science and Technology Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology

Two-dimensional materials with coexisting multifunctional properties offer platforms for revealing multifield coupling physics in both lower dimension and symmetry, and enable the potential application demand for multifunctional devices in nanoelectronics. Preceding theoretical and experimental investigations show that layered metal oxyhalides (MOX) have diverse functional properties such as the visible-light-active photocatalyst in Bi-based system as well as the magnetic and electron-correlated properties in transition-metal-based regime. Here, applying first-principles calculations and time-dependent perturbation theory, we identify that GaOCl monolayer has intrinsically multiple functional characteristics including high-temperature ferroelectricity, superferroelasticity, and strong deep-ultraviolet nonlinear optical response. Our calculations indicate that GaOCl monolayer has a ultrawide direct band gap comparable with the third-generation semiconductors, a moderate energy barrier of ferroelectric polarization reversal but with a high Curie temperature, a superferroelasticity attributed to the largely tunable ionic radius ration of Ga3+ and O2−, and remarkable nonlinear shift and injection currents inside deep-ultraviolet frequencies. These intrinsical multifunctional properties render GaOCl monolayer possible applications on ultrathin multifunctional nanoelectronics such as integrated multiferroic devices and ultraviolet optoelectronic devices.

关键词： Electronic structure Ferroelectricity Photogalvanic effect 2-dimensional systems Density functional calculations

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Full particle-in-cell simulation of the formation and structure of a collisional plasma shock wave

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Physical Review E 2021年第2期103卷 023213-023213页

作者： Wen-shuai Zhang Hong-bo Cai Bao Du Dong-guo Kang Shi-yang Zou Shao-ping Zhu Institute of Applied Physics and Computational Mathematics Beijing 100094 China

The formation and structure of a collisional shock wave in a fully ionized plasma is studied via full particle-in-cell simulations, which allows the complex momentum and energy transfer processes between different charged particles to be treated self-consistently. The kinetic energy of the plasma flow drifting towards a reflecting piston is found to be rapidly converted into thermal motion under the cooperative effects of ion-ion collisions, ion-electron collisions, and electric field charged-particle interactions. The subsequent shock evolution is influenced by the “precursor” ion beam before a quasisteady state is reached. The shock wave structure is then analyzed from a two-fluid transport viewpoint, which is found to be affected by “flux-limiting” electron transport, the nonthermal ions, and the charge separation electric field.

关键词： Shock waves & discontinuities in plasma

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A composite ansatz for the calculation of dynamical structure factor

arXiv

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arXiv 2023年

作者： Zhang, Yupei Mo, Chongjie Zhang, Ping Kang, Wei HEDPS Center for Applied Physics and Technology School of Physics Peking University Beijing100871 China Beijing Computational Science Research Center Beijing100193 China Institute of Applied Physics and Computational Mathematics Beijing100088 China HEDPS Center for Applied Physics and Technology College of Engineering Peking University Beijing100871 China

We propose an ansatz without adjustable parameters for the calculation of dynamical structure factor. The ansatz combines quasi-particle Green’s function, especially the contribution from the renormalization factor, and the exchange-correlation kernel from time-dependent density functional theory together, verified for typical metals and semiconductors from plasmon excitation regime to Compton scattering regime. It has the capability to reconcile both small-angle and large-angle x-ray scattering (IXS) signals with much improved accuracy, which can be used, as the theoretical base model, in inversely inferring electronic structures of condensed matter from IXS experimental signals directly. It may also used to diagnose thermal parameters, such as temperature and density, of dense plasmas in x-ray Thomson scattering experiments. Copyright © 2023, The Authors. All rights reserved.

关键词： Electronic structure

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computational inverse scattering with internal sources: A reproducing kernel Hilbert space approach

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Physical Review E 2024年第6期110卷 065302-065302页

作者： Yakun Dong Kamran Sadiq Otmar Scherzer John C. Schotland Faculty of Mathematics University of Vienna Oskar-Morgenstern-Platz 1 A-1090 Vienna Austria Johann Radon Institute for Computational and Applied Mathematics (RICAM) Altenbergerstraße 69 A-4040 Linz Austria Christian Doppler Laboratory for Mathematical Modeling and Simulation of Next Generations of Ultrasound Devices (MaMSi) Oskar-Morgenstern-Platz 1 A-1090 Vienna Austria and Johann Radon Institute for Computational and Applied Mathematics (RICAM) Altenbergerstrasse 69 A-4040 Linz Austria Department of Mathematics and Department of Physics Yale University New Haven Connecticut 06520-8283 USA

We present a method to reconstruct the dielectric susceptibility (scattering potential) of an inhomogeneous scattering medium, based on the solution to the inverse scattering problem with internal sources. We consider a scalar model of light propagation in the medium. We employ the theory of reproducing kernel Hilbert spaces, together with regularization to recover the susceptibility of two- and three-dimensional scattering media. Numerical examples illustrate the effectiveness of the proposed reconstruction method.

关键词： Vector spaces

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Monte Carlo Simulation of the Impact on Free Radical Yields Under Ultra-High Dose Rate Irradiation

SSRN

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SSRN 2024年

作者： Xie, Rong Hao, JianHong Xue, BiXi Zhao, Qiang Zhang, Fang Fan, JieQing Dong, ZhiWei School of Electrical and Electronic Engineering North China Electric Power University Beijing102206 China Institute of Applied Physics and Computational Mathematics Beijing100094 China

Ultra-high dose rate (UHDR) irradiation, an emerging approach in radiotherapy, has gained considerable attention due to its distinctive FLASH biological effects. A hypothesis suggests that the FLASH effect may result from changes in free radical yields caused by UHDR irradiation. In this study, Geant4-DNA was employed to simulate the generation of reactive oxygen species (ROS) radicals under UHDR conditions. To enhance simulation accuracy and extend the time scale, the compartment-based model was applied to the irradiated region, accelerating calculations during the chemical reaction stage. This model enabled the simulation of water radiolysis on a millisecond scale, allowing for a comparative analysis of the effects of initial oxygen concentration and temperature on ROS yields during the chemical reaction stage. The results demonstrate that initial oxygen concentration significantly influences subsequent free radical reactions. Higher oxygen levels accelerate the depletion of hydrogen atoms (H) and hydrated electrons (e−aq), resulting in an increased production of ROS such as hydroxyl radicals (OH), hydroperoxyl radicals (HO2), and superoxide anions (O2−), thereby elevating the risk of cellular damage. In contrast, low levels of oxygen environments may confer protective effects on cells. Additionally, temperature plays a crucial role in totally diffusion-controlled chemical reactions. As temperature rises, the yield of H radicals increases, enhancing their interaction with oxygen molecules (O2), which raises the production of HO2 while reducing the yield of O2−. The results of this study demonstrate that cellular oxygen concentration and temperature conditions significantly influence the production and consumption of ROS (OH, HO2, O2−). These findings offer valuable insights for investigating differences in cellular radiation sensitivity under various biological conditions, assisting researchers in designing more precise radiotherapy protocols and enhancing the the

关键词： Radiolysis

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Modeling the high-pressure solid and liquid phases of tin from deep potentials with ab initio accuracy

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Physical Review Materials 2023年第5期7卷 053603-053603页

作者： Tao Chen Fengbo Yuan Jianchuan Liu Huayun Geng Linfeng Zhang Han Wang Mohan Chen HEDPS CAPT College of Engineering and School of Physics Peking University Beijing 100871 People's Republic of China National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid Physics CAEP P.O. Box 919-102 Mianyang 621900 Sichuan People's Republic of China AI for Science Institute Beijing 100080 People's Republic of China DP Technology Beijing 100080 People's Republic of China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100094 People's Republic of China

Constructing an accurate atomistic model for the high-pressure phases of tin (Sn) is challenging because the properties of Sn are sensitive to pressures. We develop machine-learning-based deep potentials for Sn with pressures ranging from 0 to 50 GPa and temperatures ranging from 0 to 2000 K. In particular, we find the deep potential, which is obtained by training the ab initio data from density functional theory calculations with the state-of-the-art SCAN exchange-correlation functional, is suitable to characterize high-pressure phases of Sn. We systematically validate several structural and elastic properties of the α (diamond structure), β, bct, and bcc structures of Sn, as well as the structural and dynamic properties of liquid Sn. The thermodynamics integration method is further utilized to compute the free energies of the α, β, bct, and liquid phases, from which the deep potential successfully predicts the phase diagram of Sn including the existence of the triple-point that qualitatively agrees with the experiment.

关键词： High-pressure studies Phase diagrams Elemental metals Deep learning Density functional calculations Machine learning Meta-GGA Molecular dynamics

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Layer Coherence Origin of Intrinsic Planar Hall Effect in 2D Limit

arXiv

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arXiv 2024年

作者： Zheng, Huiyuan Zhai, Dawei Xiao, Cong Yao, Wang New Cornerstone Science Laboratory Department of Physics University of Hong Kong Hong Kong HKU-UCAS Joint Institute of Theoretical and Computational Physics Hong Kong Institute of Applied Physics and Materials Engineering University of Macau Taipa China

The intrinsic planar Hall effect has attracted intensive interest inspired by recent experiments. Existing theories of this effect require three dimensional orbital motion, or strong spin-orbit coupling of certain forms, which do not exist in van der Waals thin films. Here, we uncover a new origin of the planar Hall effect - as an intrinsic property of layer coherent electrons - that allows its presence even in bilayer and trilayer atomically thin limit. As examples, we show that the effect can be triggered by strain and interlayer sliding respectively in twisted bilayer graphene and trilayer transition metal dichalcogenides, where the effect features rich tunability and even stronger magnitude than those induced by topological nodal structures in bulk materials. The layer mechanism also provides a new route towards quantized Hall response upon a topological phase transition induced by in-plane magnetic field. These results unveil the unexplored potential of quantum layertronics and moiré flat band for planar Hall transport. Copyright © 2024, The Authors. All rights reserved.

关键词： Transition metals

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Local regularity properties for ID mixed nonlinear Schrodinger equations on half-line

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Frontiers of mathematics in China 2020年第6期15卷 1121-1142页

作者： Boling GUO Jun WU Institute of Applied Physics and Computational Mathematics Beijing 100088China Graduate School of China Academy of Engineering Physics Beijing 100088China

The main purpose of this paper is to consider the initial-boundary value problem for the 1D mixed nonlinear Schrodinger equation ut=iαu_(xx)+βu^(2)u_(x)+γ|u|^(2)u_(x)+i|u|^(2)u on the half-line with inhomogeneous boundary *** combine Laplace transform method with restricted norm method to prove the local well-posedness and continuous dependence on initial and boundary data in low regularity Sobolev ***,we show that the nonlinear part of the solution on the half-line is smoother than the initial data.

关键词： Mixed nonlinear Schrodinger(MNLS)equations initial-boundary value problem(IBVP) Bourgain spaces local well-posedness

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INVARIANT MEASURES AND THEIR LIMITING BEHAVIOR OF THE LANDAU-LIFSHITZ-BLOCH EQUATION IN UNBOUNDED DOMAINS

arXiv

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arXiv 2024年

作者： Huang, Daiwen Qiu, Zhaoyang Wang, Bixiang Institute of Applied Physics and Computational Mathematics Beijing100088 China School of Applied Mathematics Nanjing University of Finance and Economics Nanjing210046 China Department of Mathematics New Mexico Institute of Mining and Technology SocorroNM87801 United States

This paper deals with the existence and limiting behavior of invariant measures of the stochastic Landau-Lifshitz-Bloch equation driven by linear multiplicative noise and additive noise defined in the entire space d for d = 1, 2, which describes the phase spins in ferromagnetic materials around the Curie temperature. We first establish the existence and uniqueness of solutions by a domain expansion method. We then prove the existence of invariant measures by the weakly Feller argument. In the case d = 1, we show the uniform tightness of the set of all invariant measures of the stochastic equation, and prove any limit of a sequence of invariant measures of the perturbed equation must be an invariant measure of the limiting system. The cut-off arguments, stopping time techniques and uniform tail-ends estimates of solutions are developed to overcome the difficulty caused by the high-order nonlinearity and the non-compactness of Sobolev embeddings in unbounded domains. Copyright © 2024, The Authors. All rights reserved.

关键词： Additive noise

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Electronic processes in collisions between nitrogen ions and hydrogen atoms

arXiv

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arXiv 2024年

作者： Jia, C.C. Qi, Y.Y. Niu, J.J. Wu, Y. Wang, J.G. Dubois, A. Sisourat, N. Gao, J.W. School of Physics Hangzhou Normal University Hangzhou311121 China Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China Sorbonne Université CNRS UMR 7614 Laboratoire de Chimie Physique-Matière et Rayonnement Paris75005 France College of Data Science Jiaxing University Jiaxing314001 China

In order to interpret and predict the behavior and properties of fusion plasma, accurate cross sections for electronic processes in collisions between plasma impurities and atomic hydrogen are required. In this work, we investigate the electron capture (or charge exchange), target excitation, and ionization processes occurring in collision of N4+ with atomic hydrogen in a broad energy domain ranging from 0.06 to 225 keV/u. We consider N4+ ground state N4+(2s) and also N4+(2p) since the impurities in the edge plasma environment may be excited due to collisions with electrons and ions/atoms. Total and partial cross sections in both spin-averaged and spin-resolved cases are calculated using a two-active-electron semiclassical asymptotic-state close-coupling approach. For electron capture cross sections the present results show the best overall agreement with available experimental data for both total and partial cross sections, and the origins of observed discrepancies are discussed. Furthermore, we provide new data for target excitation and ionization processes, which are essential to improve our understanding of this relevant collision system. © 2024, CC BY.

关键词： Ground state

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