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The hcp-bcc transition of Be via anisotropy of modulus and sound velocity

Chinese physics B 2024年第11期33卷 361-366页

作者： Zhen Yang Jia-Wei Xian Xing-Yu Gao Fu-Yang Tian Hai-Feng Song Institute of Applied Physics University of Science and Technology BeijingBeijing 100083China National Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China

Based on ab initio calculations,we utilize the mean-field potential approach with the quantum modification in conjunction with stress–strain relation to investigate the elastic anisotropies and sound velocities of hcp and bcc Be under high-temperature(0–6000 K)and high-pressure(0–500 GPa)*** propose a general definition of anisotropy for elastic moduli and sound *** suggest that the elastic anisotropy of Be is more significantly influenced by pressure than by *** pressure-induced increase of c/a ratio makes the anisotropy of hcp Be significantly ***,the hcp Be still exhibits smaller anisotropy than bcc Be in terms of elastic moduli and sound *** suggest that measuring the anisotropy in shear sound velocity may be an approach to distinguishing the hcp–bcc phase transition under extreme conditions.

关键词： anisotropy phase transition elastic and sound properties mean-field potential

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Ionization Potential Depression Model for Warm/Hot and Dense Plasmas

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Chinese physics Letters 2024年第8期41卷 45-57页

作者： Chensheng Wu Fuyang Zhou Jun Yan Xiang Gao Yong Wu Chunhua Zeng Jianguo Wang Institute of Applied Physics and Computational Mathematics Beijing 100088China Faculty of Science Kunming University of Science and TechnologyKunming 650500China

For warm/hot and dense plasmas(WDPs),ionization potential depression(IPD)plays a crucial role in determining its ionization balance and understanding the resultant microscopic plasma properties.A sophisticated and unified IPD model is necessary to resolve those existing discrepancies between theoretical and experimental ***,the applicability of those widely used IPD models nowadays is limited,especially for the nonlocal thermodynamic equilibrium(non-LTE)dense plasma produced by short-pulse *** this work,we propose an IPD model that considers inelastic atomic processes,in which three-body recombination and collision ionization processes are found to play a crucial role in determining the electron distribution and IPD for a *** IPD model is validated by reproducing latest experimental results of Al plasmas with a wide-range condition of 70 eV–700 eV temperature and 0.2–3 times solid density,as well as a typical non-LTE system of hollow Al *** is demonstrated that the present IPD model has a significant temperature dependence due to the consideration of the inelastic collision *** a lower computational cost and wider application range of plasma conditions,the proposed model is expected to provide a promising tool to study the ionization balance and the atomic processes,as well as the related radiation and particle transports properties of the WDP.

关键词： properties. collision determining

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A Composite Ansatz for Calculation of Dynamical Structure Factor

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Chinese physics Letters 2024年第1期41卷 92-103页

作者：张玉佩莫崇杰张平康炜 HEDPS Center for Applied Physics and Technologyand School of PhysicsPeking UniversityBeijing 100871China Beijing Computational Science Research Center Beijing 100193China Institute of Applied Physics and Computational Mathematics Beijing 100088China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

We propose an ansatz without adjustable parameters for the calculation of a dynamical structure *** ansatz combines the 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 a plasmon excitation regime to the Compton scattering *** has the capability to reconcile both small-angle and large-angle inelastic x-ray scattering(IXS)signals with muchimproved accuracy,which can be used as the theoretical base model,in inversely inferring electronic structures of condensed matter from IXS experimental signals *** may also be used to diagnose thermal parameters,such as temperature and density,of dense plasmas in x-ray Thomson scattering experiments.

关键词： excitation inverse verified

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Dynamic mode decomposition of nonequilibrium electron-phonon dynamics:accelerating the firstprinciples real-time Boltzmann equation

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npj Computational Materials 2024年第1期10卷 1970-1977页

作者： Ivan Maliyov Jia Yin Jia Yao Chao Yang Marco Bernardi Department of Applied Physics and Materials Science California Institute of TechnologyPasadenaCA 91125USA Applied Mathematics and Computational Research Division Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA Department of Physics California Institute of TechnologyPasadenaCA 91125USA

Nonequilibrium dynamics governed by electron–phonon(e-ph)interactions plays a key role in electronic devices and spectroscopies and is central to understanding electronic excitations in *** real-time Boltzmann transport equation(rt-BTE)with collision processes computed from first principles can describe the coupled dynamics of electrons and atomic vibrations(phonons).Yet,a bottleneck of these simulations is the calculation of e–ph scattering integrals on dense momentum grids at each time *** we show a data-driven approach based on dynamic mode decomposition(DMD)that can accelerate the time propagation of the rt-BTE and identify dominant electronic *** apply this approach to two case studies,high-field charge transport and ultrafast excited electron *** both cases,simulating only a short time window of~10%of the dynamics suffices to predict the dynamics from initial excitation to steady state using DMD *** of the momentum-space modes extracted from DMD sheds light on the microscopic mechanisms governing electron relaxation to a steady state or *** combination of accuracy and efficiency makes our DMD-based method a valuable tool for investigating ultrafast dynamics in a wide range of materials.

关键词： materials dynamics phonon

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Spectroscopy and molecule opacity investigation on excited states of SiS

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Chinese physics B 2024年第5期33卷 381-387页

作者：李瑞吕浩男桑纪群刘晓华梁桂颖吴勇 College of Teacher Education Qiqihar UniversityQiqihar 161006China National Key Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Department of Physics College of ScienceQiqihar UniversityQiqihar 161006China School of Data Science and Artificial Intelligence Jilin Engineering Normal UniversityChangchun 130052China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100084China

The SiS molecule,which plays a significant role in space,has attracted a great deal of attention for many *** to complex interactions among its low-lying electronic states,precise information regarding the molecular structure of SiS is *** obtain accurate information about the structure of its excited states,the high-precision multireference configuration interaction(MRCI)method has been *** method is used to calculate the potential energy curves(PECs)of the 18Λ–S states corresponding to the lowest dissociation limit of *** core–valence correlation effect,Davidson’s correction and the scalar relativistic effect are also included to guarantee the precision of the MRCI *** on the calculated PECs,the spectroscopic constants of quasi-bound and bound electronic states are calculated and they are in accordance with previous experimental *** transition dipole moments(TDMs)and dipole moments(DMs)are determined by the MRCI *** addition,the abrupt variations of the DMs for the 1^(5)Σ^(+)and 2^(5)Σ^(+)states at the avoided crossing point are attributed to the variation of the electronic *** opacity of SiS at a pressure of 100 atms is presented across a series of *** increasing temperature,the expanding population of excited states blurs the band boundaries.

关键词： SiS opacity excited state spectroscopic constant configuration interaction

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A CELL-CENTERED GODUNOV METHOD BASED ON STAGGERED data DISTRIBUTION,PART Ⅰ:ONE-DIMENSIONAL CASE

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Journal of Computational mathematics 2024年第4期42卷 1172-1196页

作者： Jiayin Zhai Xiao Li Zhijun Shen Institute of Applied Physics and Computational Mathematics LCPP.O.Box 8009-26Beijing 100088China College of Big Data and Internet Shenzhen Technology UniversityShenzhen 518118China Center for Applied Physics and Technology HEDPSPeking UniversityChina

This paper presents a cell-centered Godunov method based on staggered data distribu-tion in Eulerian *** motivation is to reduce the intrinsic entropy dissipation of classical Godunov methods in the calculation of an isentropic or rarefaction *** the same time,the property of accurate shock capturing is also *** analyzing the factors that cause nonphysical entropy in the conventional Godunov methods,we introduce two velocities rather than a single velocity in a cell to reduce kinetic energy dissipation.A series of redistribution strategies are adopted to update subcell quantities in order to improve *** examples validate that the present method can dramatically reduce nonphysical entropy *** subject classification:35Q35,76N15,76M12.

关键词： Godunov method Riemann solver Rarefaction wave Nonphysical entropy increase.

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Correlation-aware probabilistic data summarization for large-scale multi-block scientific data visualization

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Computational Visual Media 2023年第3期9卷 513-529页

作者： Yang Yang Kecheng Lu Yu Wu Yunhai Wang Yi Cao Institute of Applied Physics and Computational Mathematics Beijing 100094China School of Computer Science and Technology Shandong UniversityQingdao 266237China

In this paper,we propose a correlationaware probabilistic data summarization technique to efficiently analyze and visualize large-scale multi-block volume data generated by massively parallel scientific *** core of our technique is correlation modeling of distribution representations of adjacent data blocks using copula functions and accurate data value estimation by combining numerical information,spatial location,and correlation distribution using Bayes’*** effectively preserves statistical properties without merging data blocks in different parallel computing nodes and repartitioning them,thus significantly reducing the computational ***,this enables reconstruction of the original data more accurately than existing *** demonstrate the effectiveness of our technique using six datasets,with the largest having one billion grid *** experimental results show that our approach reduces the data storage cost by approximately one order of magnitude compared to state-of-the-art methods while providing a higher reconstruction accuracy at a lower computational cost.

关键词： correlation-awareness large-scale data multi-block methods probabilistic data summarization

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Phase-field simulations of the effect of temperature and interface for zirconiumδ-hydrides

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Chinese physics B 2024年第4期33卷 701-710页

作者：陈子航盛杰刘瑜施小明黄厚兵许可王越超武帅孙博刘海风宋海峰 School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Advanced Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Department of Physics University of Science and Technology BeijingBeijing 100083China

Hydride precipitation in zirconium cladding materials can damage their integrity and *** temperature and material defects have a significant effect on the dynamic growth of *** this study,we have developed a phasefield model based on the assumption of elastic behaviour within a specific temperature range(613 K-653 K).This model allows us to study the influence of temperature and interfacial effects on the morphology,stress,and average growth rate of zirconium *** results suggest that changes in temperature and interfacial energy influence the length-to-thickness ratio and average growth rate of the hydride *** ultimate determinant of hydride orientation is the loss of interfacial coherency,primarily induced by interfacial dislocation defects and quantifiable by the mismatch degree *** escalation in interfacial coherency loss leads to a transition of hydride growth from horizontal to vertical,accompanied by the onset of redirection ***,redirection occurs at a critical mismatch level,denoted as qc,and remains unaffected by variations in temperature and interfacial ***,this redirection leads to an increase in the maximum stress,which may influence the direction of hydride crack *** research highlights the importance of interfacial coherency and provides valuable insights into the morphology and growth kinetics of hydrides in zirconium alloys.

关键词： zirconium hydride phase-field method temperature effect mismatch degree

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Strong Overall Error Analysis for the Training of Artificial Neural Networks Via Random Initializations

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Communications in mathematics and Statistics 2024年第3期12卷 385-434页

作者： Arnulf Jentzen Adrian Riekert School of Data Science and Shenzhen Research Institute of Big Data The Chinese University of Hong KongShenzhenPeople’s Republic of China Applied Mathematics:Institute for Analysis and Numerics University of MünsterMünsterGermany

Although deep learning-based approximation algorithms have been applied very successfully to numerous problems,at the moment the reasons for their performance are not entirely understood from a mathematical point of ***,estimates for the convergence of the overall error have been obtained in the situation of deep supervised learning,but with an extremely slow rate of *** this note,we partially improve on these *** specifically,we show that the depth of the neural network only needs to increase much slower in order to obtain the same rate of *** results hold in the case of an arbitrary stochastic optimization algorithm with *** initializations.

关键词： Deep learning Artificial intelligence Empirical risk minimization Optimization

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Faithful geometric measures for genuine tripartite entanglement

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Physical Review A 2024年第1期110卷 L010402-L010402页

作者： Xiaozhen Ge Lijun Liu Yong Wang Yu Xiang Guofeng Zhang Li Li Shuming Cheng Department of Control Science and Engineering Department of Applied Mathematics The Department of Mathematics and Computer Science State Key Laboratory for Mesoscopic Physics School of Physics Frontiers Science Center for Nano-optoelectronics and Collaborative Innovation Center of Quantum Matter Shanghai Institute of Intelligent Science and Technology Institute for Advanced Study

We present a faithful geometric picture for genuine tripartite entanglement of discrete, continuous, and hybrid quantum systems. We first find that the triangle relation Ei|jkα≤Ej|ikα+Ek|ijα holds for all subadditive bipartite entanglement measure E, all permutations under parties i,j,k, all α∈[0,1], and all pure tripartite states. Then, we rigorously prove that the nonobtuse triangle area, enclosed by side Eα with 0<α≤1/2, is a measure for genuine tripartite entanglement. Finally, it is significantly strengthened for qubits that given a set of subadditive and nonsubadditive measures, some state is always found to violate the triangle relation for any α>1, and the triangle area is not a measure for any α>1/2. Our results pave the way to study discrete and continuous multipartite entanglement within a unified framework.

关键词： Entanglement measures Quantum correlations in quantum information Quantum correlations, foundations & formalism Resource theories

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