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Dynamics of particles near the surface of amedium under ultra-strong shocks

Matter and Radiation at Extremes 2021年第2期6卷 46-53页

作者： Zixiang Yan Hao Liu Xinyu Zhang Guoli Ren Jie Liu Wei Kang Weiyan Zhang Xiantu He HEDPS Center for Applied Physics and Technologyand School of PhysicsPeking UniversityBeijing 100871China Department of Applied Physics School of Physics and ElectronicsHunan UniversityChangsha 410082China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China Institute of Applied Physics and Computational Mathematics Beijing 100088China Graduate School China Academy of Engineering PhysicsBeijing 100193China China Academy of Engineering Physics Mianyang 621900China

Through nonequilibrium molecular dynamics simulations,we provide an atomic-scale picture of the dynamics of particles near the surface of a medium under ultra-strong *** shows that the measured surface velocity v_(f)under ultra-strong shocks is actually the velocity of the critical surface at which the incident probe light is reflected,and v_(f)has a single-peaked *** doubling rule commonly used in the case of relatively weak shocks to determine particle velocity behind the shock front is generally not valid under ultra-strong *** a short period of acceleration,v_(f)exhibits a long slowly decaying tail,which is not sensitive to the atomic mass of the medium.A scaling law for v_(f)is also proposed,and this may be used to improve the measurement of particle velocity u in future experiments.

关键词： structure. surface doubling

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Ferromagnetic impurity induced Majorana zero mode in iron-based superconductors

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Physical Review B 2022年第18期106卷 L180504-L180504页

作者： Rui Song Ping Zhang Xian-Tu He Ning Hao HEDPS Center for Applied Physics and Technology and School of Physics Peking University Beijing 100871 China HEDPS Center for Applied Physics and Technology and School of Engineering Peking University Beijing 100871 China Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field Laboratory HFIPS Anhui Chinese Academy of Sciences and University of Science and Technology of China Hefei 230031 China School of Physics and Physical Engineering Qufu Normal University Qufu 273165 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China

Recent experiments reported the puzzling zero-energy modes associated with ferromagnetic impurities in some iron-based superconductors with topological band structures. Here, we show that a sufficiently strong exchange coupling between a ferromagnetic impurity and a substrate can trigger a quantum phase transition, beyond which the phase of the topological surface superconducting order parameter around the impurity acquires a sign change. In such a case, we prove that besides a pair of impurity induced trivial Yu-Shiba-Rusinov states, a degenerate pair of Majorana modes can be induced at the boundary separating the two sign-change regimes and trapped around the impurity in the topological surface superconducting state. Furthermore, we show that our theory can explain the controversial observations and confusing features of the zero-energy modes from recent experiments in some iron-based superconductors.

关键词： First-principles calculations Superconductivity Topological superconductors Iron-based superconductors

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Interface Width Effect on the Weakly Nonlinear Rayleigh–Taylor Instability in Spherical Geometry

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Chinese physics Letters 2020年第7期37卷 43-46页

作者： Yun-Peng Yang Jing Zhang Zhi-Yuan Li Li-Feng Wang Jun-Feng Wu Wun-Hua Ye Xian-Tu He School of Physics Peking UniversityBeijing 100871China Center for Applied Physics and Technology HEDPSand College of EngineeringPeking UniversityBeijing 100871China Institute of Applied Physics and Computational Mathematics Beijing 100094China

Interface width effect on the spherical Rayleigh–Taylor instability in the weakly nonlinear regime is studied by numerical *** Legendre perturbation mode Pn with wave number Kn and interface half-width L,the commonly adopted empirical linear growth rate formulaγnem(L)=γn/√1+KnL is found to be sufficient in spherical *** the weakly nonlinear stage,the interface width affects the mode coupling *** development of the mode P2n is substantially influenced by the interface ***,the nonlinear saturation amplitude increases with the interface width.

关键词： interface nonlinear weakly

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Molecular Opacity Calculations for Lithium Hydride at Low Temperature

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Chinese physics Letters 2020年第12期37卷 24-30页

作者： Gui-Ying Liang Yi-Geng Peng Rui Li Yong Wu Jian-Guo Wang Institute of Applied Physics and Computational Mathematics Beijing 100088China Department of Applied Physics Nanjing University of Science and TechnologyNanjing 210094China Department of Physics College of ScienceQiqihar UniversityQiqihar 161006China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100084China

The opacities of the lithium hydride molecule are calculated for temperatures of 300 K,1000 K,1500 K,and 2000 K,at a pressure of 10 atm,in which the contributions from the five low-lying electronic states are *** ab initio multi-reference single and double excitation configuration interaction(MRDCI)method is applied to compute the potential energy curves(PECs)of the 7 LiH,including four 1∑+states and one 1Πstate,as well as the corresponding transition dipole moments between these *** ro-vibrational energy levels are calculated based on the PECs obtained,together with the spectroscopic *** addition,the partition functions are also computed,and are provided at temperatures ranging from 10 K to 2000 K for 7 LiH,7 LiD,6 LiH,and 6 LiD.

关键词： Lithium hydride partition

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Multi-Phase-Field Method for Heterogeneous Brittle Material with Reduced-Order-Homogenization

SSRN

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SSRN 2024年

作者： Liu, Nianqi Yuan, Zifeng HEDPS Center for Applied Physics and Technology Department of Mechanics and Engineering Science Peking University Beijing100871 China State Key Laboratory for Turbulence and Complex Systems Peking University Beijing100871 China

This manuscript proposes a novel multiscale multi-phase-field method based on reduced-order-homogenization (ROH) approach to investigate the damage initiation and crack evolution for the composites, namely the Ms-PFM. Unlike many existing multi-phase-field methods that are applied to fiber reinforced composites which consist of two different phases, the Ms-PFM can handle any number of phase fields. In the Ms-PFM, each phase of the composite has its phase field. The composite's overall response is then obtained by averaging and homogenization approaches through the ROH framework in order to obtain the macroscopic stress and consistent material moduli. In the present work, we derive the governing equations in terms of the displacement field and each phase field. Through the ROH and the Francfort-Marigo variational principle, we can obtain the governing elliptical partial differential equation for each phase field regarding the stress states of different phases of the composites. Through the Ms-PFM, we can identify the damage mechanism at the microscale and simultaneously predict the macroscale load-deformation response. The corresponding weak form is derived, and the numerical algorithm through the finite element method is derived as well. Finally, several sets of numerical examples are adopted to verify the Ms-PFM. The damage evolution predicted by the Ms-PFM shows good agreement with the experiments. © 2024, The Authors. All rights reserved.

关键词： Numerical methods

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Electron capture and target excitation in intermediate-energy He+−H collisions

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Physical Review A 2024年第1期109卷 012801-012801页

作者： J. W. Gao Y. Y. Qi Y. Wu J. G. Wang N. Sisourat A. Dubois School of Physics Hangzhou Normal University 311121 Hangzhou China College of Data Science Jiaxing University Jiaxing 314001 China Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics 100088 Beijing China Center for Applied Physics and Technology HEDPS Peking University 100871 Beijing China Sorbonne Université CNRS UMR 7614 Laboratoire de Chimie Physique-Matière et Rayonnement 75005 Paris France

We present all-electron close-coupling calculations of cross sections for electron capture and target excitation occurring in 0.25–200 keV/u He+−H collisions. We show overall good agreements with available experimental data for total electron capture, n=2 target excitation, and related Hα emission. We especially focus on nℓ-selective capture and excitation processes and critically compare our results with those from previous theoretical investigations. Our results confirm the oscillatory structures observed in the spin-averaged H(2s) and H(2p) excitation cross sections for impact energies below 50 keV/u. Furthermore, we interpret these oscillations as the consequence of interferences between excitation to H(2s) and H(2p0) in both spin-singlet and spin-triplet symmetries, as well as between electron capture to He(1s2p1P, |ML|=1) and excitation to H(2p1) in spin-singlet symmetry.

关键词： Atomic & molecular collisions Charge-transfer collisions

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Detailed and Reduced Chemical Kinetic Model of Ch4/O2 Combustion Based on High-Precision First Principles Molecular Dynamics Simulation

SSRN

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SSRN 2023年

作者： Zhang, Teng Shou, Liefeng Chen, Lang Wang, Hongliang Long, Yao Wang, Zhongqi Chen, Jun Beijing Institute of Technology Beijing100081 China Northwest Institute of Nuclear Technology Xi'An710024 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China HEDPS Center for Applied Physics and Technology College of Engineering Peking University Beijing100871 China

CH4/O2 combustion reaction kinetics have been attracting many research interests, because of its potential application in engineering field. In this work, the combustion reaction of CH4/O2 at high temperature is simulated based on the first-principles molecular dynamics method first time. Two new intermediates, HCOOH and O3, and their effect to the formation of CO2 and OH radical are revealed. Our elementary reaction analysis also discovered that radical, OH, HO2 and others, play a key role in combustion process. They act as high active oxidant and promote final products formation. Combining elementary reaction with simplifying technique, a novel 30-step reduced chemical kinetic model is constructed. It is also successful verified by comparing simulation value with experimental ignition delay time, laminar flame speed, adiabatic flame temperature and CJ detonation velocity of CH4 combustion. This work is an implementation of the scheme of "first-principle model construction + model simplification + engineering verification". It also indicated the feasibility of this scheme to establish reduced chemical kinetic model of fuel/oxidant or energetic materials in future. © 2023, The Authors. All rights reserved.

关键词： Reaction kinetics

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Differential and integral cross sections for the valence-shell excitations in D2O studied by fast electron impact

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Physical Review A 2022年第6期105卷 062817-062817页

作者： Zi-Ru Ma Shu-Xing Wang Yi-Geng Peng Jian-Hui Zhu Yuan-Chen Xu Xiao-Jiao Du Li-Han Wang Wei-Qing Xu Yong Wu Jian-Guo Wang Lin-Fan Zhu Department of Modern Physics University of Science and Technology of China Hefei Anhui 230026 China Department of Applied Physics Nanjing University of Science and Technology Nanjing 210094 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China Center for Transformative Science ShanghaiTech University Shanghai 201210 China HEDPS Center for Applied Physics and Technology and College of Engineering Peking University Beijing 100871 China

The experimental generalized oscillator strengths (GOSs) for the valence-shell excitations of heavy water in 6.50–12.17 eV are determined by fast electron scattering with an incident electron energy of 1500 eV and an energy resolution of 80 meV. The experimental data of the Ã1B1←X̃1A1 transition between H2O and D2O show significant discrepancies around the minimum, and further theoretical calculations with nuclear effects accounted are recommended. The comparisons of the present GOSs of Ã1B1←X̃1A1 and B̃1A1←X̃1A1 transitions in D2O with theoretical calculations within the first Born approximation and the second Born approximation indicate that the higher Born terms become prominent at large momentum transfers. In particular, the GOSs of the dipole-forbidden transition 1A2←X̃1A1 are extracted, benefiting from the present high-energy electron scattering, where most of electronic dipole-forbidden transitions are not involved. By extrapolating the GOSs to the zero momentum transfer, the optical oscillator strengths for the corresponding dipole-allowed transitions are determined, which provide an independent cross-check for previous optical measurements. Moreover, the integral Born cross sections are scaled to an accurate level with the aid of the binding energy–excitation energy–scaling method. The relevant experimental data in this work can supplement the molecular database with electron collision data involving heavy water.

关键词： Atomic & molecular collisions Electronic excitation & ionization Electronic transitions

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Investigation into the improved axial compressibility of a spinning non-ideal gas

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Frontiers of physics 2020年第4期15卷 25-31页

作者： Yi-Wen Zhang Shi-Long Su Shu-Bin Xie Wei-Min Zhou Hao Liu Department of Applied Physics School of Physics and ElectronicsHunan UniversityChangsha 410082China Science and Technology on Plasma Physics Laboratory Laser Fusion Research CenterChina Academy of Engineering PhysicsMianyang 621900China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100086China

Using theoretical analysis and mumerical calculation method,the axial adiabatic compression of a spinning non-ideal gas in a cylinder with a smooth surface is *** show that the axial pressure of a spinning gas will gradually become lower than that of a stationary gas during continuous compression,even though the initial axial pressure of the spining gas is larger than that of the stationary gas at the same initial temperature and average *** phenomenon indicates that the axial compressibility of gas is improved in a rotating *** addition,the effect of different forms of virial coefficient B(T)on pressure and temperature changes in spinning and stationary gases are *** on the axial compressibility of spinning non ideal gas can provide useful references for fields that require high compression of gases,such as laser fusion,laboratory astrophysics,and Z-pinch experiments.

关键词： compressibility spinning system non ideal gas virial EOS

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Distinctive Electronic Characteristics and Ultra-high Thermoelectric Power Factor in Be-Fe Intermetallics

arXiv

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arXiv 2024年

作者： Hao, Qi D. Wang, H. Chen, Xiang R. Geng, Hua Y. College of Physics Sichuan University Chengdu610065 China National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid Physics China Academy of Engineering Physics Mianyang Sichuan621900 China HEDPS Center for Applied Physics and Technology College of Engineering Peking University Beijing100871 China

Beryllium (Be) alloys are indispensable in cutting-edge applications due to their unique advantages. However, the scientific understanding about their structure and property is deficient, which greatly restricts their applications within a narrow field. In this work, a systematic investigation on the structure and properties of Be-Fe binary was carried out with first-principles unbiased evolutionary algorithms. Five new intermetallics unreported before, including insulating Be11Fe and Be4Fe, metallic Be3Fe, and metastable BeFe and BeFe2 were discovered, among which Be11Fe has a unique clathrate structure and is an electride. Surprisingly, we found that Fe unexpectedly acts as an anion in all known Be-Fe intermetallics, and its valence state can even reach -5, leading to the complete filling of its 3d orbitals. Most of these compounds exhibiting a gap or pseudogap at the Fermi level. Specifically, the band gap is determined as 0.22 eV and 0.85 eV for Be11Fe and Be4Fe at the level of single-shot GW, respectively. This is the first report of insulating phases in Be-based intermetallics. We also discovered that Be11Fe exhibits an impressive thermoelectric power factor of 178 μW cm-1 K2 at room temperature, to our best knowledge, the highest among known semiconductors under ambient conditions, indicating its potential for waste heat harvesting and active cooling. These findings will deepen our understanding of Be-based and Fe-based compounds, and expand the application fields of Be-based alloys to a brand-new realm. © 2024, CC BY.

关键词： Energy gap

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