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Prediction of novel ordered phases in U-X (X= Zr, Sc, Ti, V, Cr, Y, Nb, Mo, Hf, Ta, W) binary alloys under high pressure

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arXiv 2024年

作者： Pan, Xiao L. Song, Hong X. Wang, H. Wu, F.C. Gan, Y.C. Chen, Xiang R. Chen, Ying Geng, Hua Y. National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid Physics China Academy of Engineering Physics Mianyang Sichuan621900 China College of Physics Sichuan University Chengdu610065 China HEDPS Center for Applied Physics and Technology College of Engineering Peking University Beijing100871 China Fracture and Reliability Research Institute School of Engineering Tohoku University Sendai980-8579 Japan

U-based binary alloys have been widely adopted in fast nuclear reactors, but their stability under extreme conditions of high-pressure is almost unknown, mounting up to latent risk in applications. Here, possible ordered phases in U-Zr system up to 200 GPa are comprehensively investigated by unbiased first-principles structure prediction. Stable U2Zr, metastable U3Zr and U4Zr phases are discovered for the first time, which exhibit strong stability under compression. They all are metallic, with 5f electrons of uranium dominating the electronic density of states near the Fermi level. Prominent ionic interactions between U and Zr atoms, as well as covalent interactions between adjacent uranium atoms, are found. The same strategy is applied to explore the stability of ordered phases in other U-based binary transition metal alloys, U-X (X= Sc, Ti, V, Cr, Y, Nb, Mo, Hf, Ta, W). Stable and metastable ordered phases similar to U-Zr alloy are unveiled, all with similar electronic structures. For these alloys, we find that the structure of U2X (X=Zr, Ti, Hf) hosts a unique hybrid phase transition similar to U2Nb, which is a superposition of a first-order transition and a second-order transition. The prediction of these novel phases not only refutes the stability of the long-believed ordered phase I4/mmm-U2Mo, but also rewrites the phase diagrams of U-X (X= Zr, Sc, Ti, V, Cr, Nb, Mo, Hf, Ta) alloys under high pressure. All of these findings promote our understanding of the high-pressure behavior of the broad category of U-based binary alloys with transition metals. © 2024, CC BY.

关键词： Binary alloys

Enhancing Strong-Field Dissociation of H2+ in Helium Nanodroplets

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Physical Review Letters 2023年第3期130卷 033201-033201页

作者： Lianrong Zhou Xiaoqing Hu Yigeng Peng Junjie Qiang Peifen Lu Kang Lin Shengzhe Pan Xiaochun Gong Wenyu Jiang Zhejun Jiang Chenxu Lu Hongcheng Ni Cheng Jin Ruifeng Lu Yong Wu Jianguo Wang Jian Wu State Key Laboratory of Precision Spectroscopy East China Normal University Shanghai 200241 China Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China Department of Applied Physics Nanjing University of Science and Technology Nanjing 210094 China Institut für Kernphysik Goethe-Universität Frankfurt am Main Frankfurt am Main 60438 Germany HEDPS Center of Applied Physics and Technology Peking University Beijing 10084 China Collaborative Innovation Center of Extreme Optics Shanxi University Shanxi 030006 China Chongqing Key Laboratory of Precision Optics Chongqing Institute of East China Normal University Chongqing 401121 China

We investigate the above-threshold multiphoton ionization of H2 embedded in superfluid He nanodroplets driven by ultraviolet femtosecond laser pulses. We find that the surrounding He atoms enhance the dissociation of in-droplet H2+ from lower vibrational states as compared to that of isolated gas-phase molecules. As a result, the discrete peaks in the photoelectron energy spectrum correlated with the HHe+ from the dissociative in-droplet molecule shift to higher energies. Based on the electron-nuclear correlation, the photoelectrons with higher energies are correlated to the nuclei of the low-vibrationally excited molecular ion as the nuclei share less photon energy. Our time-dependent nuclear wave packet quantum simulation using a simplified He−H2+ system confirms the joint contribution of the driving laser field and the neighboring He atoms to the dissociation dynamics of the solute molecular ion. The results strengthen our understanding of the role of the environment on light-induced ultrafast dynamics of molecules.

关键词： Atomic & molecular clusters Atomic & molecular processes in external fields Electronic excitation & ionization Photodissociation

Ferromagnetic Impurity Induced Majorana Zero Mode in Iron-Based Superconductor

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arXiv 2022年

作者： Song, Rui Zhang, Ping He, Xian-Tu Hao, Ning HEDPS Center for Applied Physics and Technology School of Physics Peking University Beijing100871 China HEDPS Center for Applied Physics and Technology School of Engineering Peking University Beijing100871 China Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field Laboratory HFIPS Anhui China Chinese Academy of Sciences University of Science and Technology of China Hefei China School of Physics and Physical Engineering Qufu Normal University Qufu273165 China Institute of Applied Physics and Computational Mathematics Beijing100088 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 the sufficiently strong exchange coupling between a ferromagnetic impurity and 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 a Kramers 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. Copyright © 2022, The Authors. All rights reserved.

关键词： Ferromagnetism

Dynamic stabilization and parametric excitation of instabilities in an ablation front by a temporally modulated laser pulse

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Physical Review E 2025年第5期111卷 055204-055204页

作者： K. G. Zhao J. W. Li L. F. Wang Z. Y. Li Z. H. Di C. Xue J. Q. Dong H. Zhang J. F. Wu H. B. Zhuo W. H. Ye C. T. Zhou Y. K. Ding W. Y. Zhang X. T. He Shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology Center for Intense Laser Application Technology and College of Engineering Physics Shenzhen Technology University Shenzhen 518118 People's Republic of China Institute of Applied Physics and Computational Mathematics Beijing 100094 People's Republic of China HEDPS Center for Applied Physics and Technology Peking University Beijing 100871 People's Republic of China State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and Technology Beijing 100083 People's Republic of China Shanghai Institute of Laser Plasma Shanghai 201800 People's Republic of China

We conducted a numerical study of the effects of the modulation amplitude and period of a temporally modulated laser pulse on instabilities at an ablation front. The physical features of the oscillatory acceleration and ablation velocity in unperturbed ablative flows display periodic oscillations. As the modulation amplitude or period is increased, the asymmetry of the oscillatory acceleration and ablation velocity becomes more evident, and the peak values of these quantities increase. The numerical solution of the Mathieu equation [R. Betti et al., Phys. Rev. Lett. 71, 3131 (1993)] with a fitted acceleration was used to evaluate the behaviors of the oscillatory acceleration. The spatial structure and interfacial evolution of a single-mode ablative Rayleigh-Taylor instability (ARTI) were analyzed for the modulated laser pulses with different modulation amplitudes and periods. It was also observed in a previous work [K. G. Zhao et al., Phys. Rev. E 109, 025213 (2024)] that the modulated laser exerts a stabilizing influence on the growth of the ARTI in the intermediate- and long-wavelength regions. We found that increasing either the modulation amplitude or period enhances the dynamic stabilization of the ARTI while simultaneously inducing a characteristic destabilization of the parametric instability, which may excite the short-wavelength perturbations through the parametric resonance [G. H. Wolf, Phys. Rev. Lett. 24, 444 (1970)].

关键词： Stabilization

Single- and double-electron capture in intermediate-energy Ar8+ + He collisions

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Physical Review A 2022年第4期106卷 042809-042809页

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

Single- and double-electron-capture processes occurring in Ar8+ and He collisions are investigated in a broad energy domain ranging from 0.1 to 100 keV/u. Total and partial cross sections are calculated using a two-active-electron semiclassical asymptotic-state close-coupling approach. For single-electron-capture cross sections the present results show the best overall agreement with available experimental data for both total and partial cross sections, and possible reasons for observed discrepancies are discussed. Furthermore, we extend the understanding of the electron-capture processes on that system to impact energies above 20 keV/u for which no data exist. The cross sections for double-electron-capture processes are also reported and show severe discrepancies with the rare available experimental data.

关键词： Atomic & molecular collisions Charge-transfer collisions

Obtaining Intense Attosecond Pulses in the Far Field from Relativistic Laser-Plasma Interactions

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Physical Review applied 2021年第2期16卷 024042-024042页

作者： Y. Zhang C. L. Zhong S. P. Zhu X. T. He M. Zepf B. Qiao Center for Applied Physics and Technology HEDPS and SKLNPT School of Physics Peking University Beijing 100871 China Institute of Applied Physics and Computational Mathematics Beijing 100094 China Helmholtz Institute Jena 07743 Jena Germany

In this paper, we show that the Gouy phase shift plays a key role in the far-field waveform evolution of the reflected harmonic radiations from plasma surfaces driven by a relativistic Gaussian laser. With a proper adjustment of laser focal position away from the plasma surface, the inherent separations between the peaks of different harmonic carrier waves as well as the fundamental wave due to different wavelengths can be cleared away when they propagate from near to far field, since they experience the same Gouy phase shift of π/2. Using this method, intense attosecond pulses can be obtained in the far field with no need of any spectral filters. Three-dimensional particle-in-cell simulations show that far-field attosecond pulses with intensity of 4×1015W/cm2 (2.56×1017W/sr; 65 times increase) and duration of 76as (50% decrease) can be obtained by lasers at intensities of 1021W/cm2. Such brilliant pulses with fully reserved spectra significantly benefit applications in attosecond science.

关键词： High-energy-density plasmas High-order harmonic generation Laser-plasma interactions Ultrafast phenomena X-ray generation in plasmas

Molecule opacities of X^2Σ^+, A^2Π, and B^2Σ^+ states of CS^+

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Chinese physics B 2019年第5期28卷 64-70页

作者： Xiao-He Lin Gui-Ying Liang Jian-Guo Wang Yi-Geng Peng Bin Shao Rui Li Yong Wu School of Physics Beijing Institute of Technology Institute of Applied Physics and Computational Mathematics Department of Physics College of Science Qiqihar University HEDPS Center for Applied Physics and Technology Peking University

Carbon sulfide cation(CS^+) plays a dominant role in some astrophysical atmosphere environments. In this work, the rovibrational transition lines are computed for the lowest three electronic states, in which the internally contracted multireference configuration interaction approach(MRCI) with Davison size-extensivity correction(+Q) is employed to calculate the potential curves and dipole moments, and then the vibrational energies and spectroscopic constants are extracted. The Frank–Condon factors are calculated for the bands of X^2^+Σ^+–A^2Π and X^2Σ^+–B^2Σ^+systems, and the band of X^2Σ^+–A^2Π is in good agreement with the available experimental results. Transition dipole moments and the radiative lifetimes of the low-lying three states are evaluated. The opacities of the CS^+ molecule are computed at different temperatures under the pressure of 100 atms. It is found that as temperature increases, the band systems associated with different transitions for the three states become dim because of the increased population on the vibrational states and excited electronic states at high temperature.

关键词： CS^+ dipole moment transition dipole moment opacity

Subspace method based on neural networks for eigenvalue problems

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arXiv 2024年

作者： Dai, Xiaoying Fan, Yunying Sheng, Zhiqiang LSEC Institute of Computational Mathematics and Scientific/Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing100190 China School of Mathematical Sciences University of Chinese Academy of Sciences Beijing100049 China National Key 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

With the rapid development of machine learning, numerical discretization methods based on deep neural networks have been widely used in many fields, especially in solving high-dimensional problems where traditional methods face bottlenecks. However, for low-dimensional problems, existing machine learning methods are not as accurate and efficient as traditional methods. In this paper, we propose a subspace method based on neural networks for eigenvalue problems with high accuracy and low cost. Our basic idea is to use neural network based basis functions to span a subspace, then calculate the parameters of the neural network based basis functions through appropriate training, and finally calculate the Galerkin projection of the eigenvalue problem onto the subspace and obtain an approximate solution. In addition, we reduce the dimension of the subspace by applying some dimensionality reduction technique, which can improve the accuracy of the approximate solution in further. Numerical experiments show that we can obtain approximate eigenvalues with accuracy of 10−11 but with less then 400 epochs, which is significantly superior to other existing neural network based *** Codes 65N25, 65L15, 68T07 Copyright © 2024, The Authors. All rights reserved.

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Laboratory observation of plasmoid-dominated magnetic reconnection in hybrid collisional-collisionless regime

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arXiv 2022年

作者： Zhao, Zhong Hai An, H.H. Xie, Y. Lei, Z. Yao, W.P. Yuan, W.Q. Xiong, J. Wang, C. Ye, J.J. Xie, Z.Y. Fang, Z.H. Lei, A.L. Pei, W.B. He, X.T. Zhou, W.M. Wang, W. Zhu, S.P. Qiao, B. Center For Applied Physics And Technology Hedps Sklnpt School Of Physics Peking University Beijing100871 China Shanghai Institute Of Laser Plasma Caep Shanghai201800 China Institute Of Applied Physics And Computational Mathematics Beijing100094 China Mianyang621900 China

Magnetic reconnection, breaking and reorganization of magnetic field topology, is a fundamental process for rapid release of magnetic energy into plasma particles that occurs pervasively throughout the universe. In most natural circumstances, the plasma properties on either side of the reconnection layer are asymmetric, in particular for the collision rates that are associated with a combination of density and temperature and critically determine the reconnection mechanism. To date, all laboratory experiments on magnetic reconnections have been limited to purely collisional or collisionless regimes. Here, we report a well-designed experimental investigation on asymmetric magnetic reconnections in a novel hybrid collisional-collisionless regime by interactions between laser-ablated Cu and CH plasmas. We show that the growth rate of the tearing instability in such a hybrid regime is still extremely large, resulting in rapid formation of multiple plasmoids, lower than that in the purely collisionless regime but much higher than the collisional case. In addition, we, for the first time, directly observe the topology evolutions of the whole process of plasmoid-dominated magnetic reconnections by using highly-resolved proton radiography. © 2022, CC BY.

关键词： Topology