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Accurate path-integral molecular dynamics calculation of aluminum with improved empirical ionic potentials

Physical Review B 2022年第17期106卷 174107-174107页

作者： Zixiang Yan Chunyi Zhang Xing Liu Qing Miao Ming Fang Wei Kang HEDPS Center for Applied Physics and Technology and School of Physics Peking University Beijing 100871 China HEDPS Center for Applied Physics and Technology and College of Engineering Peking University Beijing 100871 China China Institute of Nuclear Industry Strategy Beijing 100048 China China Aerodynamics Research and Development Center Mianyang 621000 China

We show that an accurate description of the interplay between the anharmonic ionic interaction and the zero-point fluctuation of ions in crystalline aluminum (Al) can be achieved using the path-integral molecular dynamics (PIMD) method in conjunction with improved empirical modified embedded-atom method (MEAM) potentials. Our results show that the zero-point fluctuation of ions is noticeable at a temperature between 200 K and 250 K, roughly half of the Al Debye temperature of 428 K, with a selective influence on mechanical properties. The effect provides appreciable corrections to the lattice constant a, bulk modulus B, and elastic constant C11 at low temperature, but without much influence on elastic constants C12 and C44. With a revised MEAM potential which takes into consideration the influence of zero-point fluctuations, the PIMD method has a much improved accuracy in a, B, and the C's up to 700 K, when compared with precision experimental measurements. The largest errors of a and B can even be reduced by about an order in percentage below 300 K.

关键词： Anharmonic lattice dynamics Elasticity Structural properties Thermal expansion Face-centered cubic Metals Embedded atom model Path-integral methods

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Interface coupling effects of weakly nonlinear Rayleigh–Taylor instability with double interfaces

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Chinese physics B 2020年第3期29卷 318-322页

作者： Zhiyuan Li Lifeng Wang Junfeng Wu Wenhua Ye Institute of Applied Physics and Computational Mathematics Beijing 100094China Center for Applied Physics and Technology HEDPSand College of EngineeringPeking UniversityBeijing 100871China

Taking the Rayleigh–Taylor instability with double interfaces as the research object,the interface coupling effects in the weakly nonlinear regime are studied *** variation of Atwood numbers on the two interfaces and the variation of the thickness between them are taken into *** is shown that,when the Atwood number on the lower interface is small,the amplitude of perturbation growth on the lower interface is positively related with the Atwood number on the upper ***,it is negatively related when the Atwood number on the lower interface is *** above phenomenon is quantitatively studied using an analytical formula and the underlying physical mechanism is presented.

关键词： Rayleigh–Taylor instability weakly nonlinear regime numerical simulation

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High-Flux Neutron Generator Based on Laser-Driven Collisionless Shock Acceleration

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Physical Review Letters 2023年第2期131卷 025101-025101页

作者： Y. L. Yao S. K. He Z. Lei T. Ye Y. Xie Z. G. Deng B. Cui W. Qi L. Yang S. P. Zhu X. T. He W. M. Zhou B. Qiao Center for Applied Physics and Technology HEDPS and State Key Laboratory of Nuclear Physics and Technology School of Physics Peking University Beijing 100871 China Science and Technology on Plasma Physics Laboratory Research Center of Laser Fusion China Academy of Engineering Physics (CAEP) Mianyang 621900 China Institute of Applied Physics and Computational Mathematics Beijing 100094 China Frontiers Science Center for Nano-optoelectronic Peking University Beijing 100094 China

A novel compact high-flux neutron generator with a pitcher-catcher configuration based on laser-driven collisionless shock acceleration (CSA) is proposed and experimentally verified. Different from those that previously relied on target normal sheath acceleration (TNSA), CSA in nature favors not only acceleration of deuterons (instead of hydrogen contaminants) but also increasing of the number of deuterons in the high-energy range, therefore having great advantages for production of high-flux neutron source. The proof-of-principle experiment has observed a typical CSA plateau feature from 2 to 6 MeV in deuteron energy spectrum and measured a forward neutron flux with yield 6.6×107 n/sr from the LiF catcher target, an order of magnitude higher than the compared TNSA case, where the laser intensity is 1019 W/cm2. Self-consistent simulations have reproduced the experimental results and predicted that a high-flux forward neutron source with yield up to 5×1010 n/sr can be obtained when laser intensity increases to 1021 W/cm2 under the same laser energy.

关键词： High-energy-density plasmas Laser driven ion acceleration Laser-plasma interactions Neutron physics Nuclear reactions Neutrons Multiscale modeling Nuclear data analysis & compilation

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Artificial neural network-based one-equation model for simulation of laminar-turbulent transitional flow

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Theoretical & applied Mechanics Letters 2023年第1期13卷 50-57页

作者： Lei Wu Bing Cui Zuoli Xiao State Key Laboratory for Turbulence and Complex Systems College of EngineeringPeking UniversityBeijing 100871China Inspur Electronic Information Industry Co. LtdBeijing 100085China HEDPS and Center for Applied Physics and Technology College of EngineeringPeking UniversityBeijing 100871China Nanchang Innovation Institute Peking UniversityNanchang 330008China

A mapping function between the Reynolds-averaged Navier-Stokes mean flow variables and transition intermittency factor is constructed by fully connected artificial neural network(ANN),which replaces the governing equation of the intermittency factor in transition-predictive Spalart-Allmaras(SA)-γ*** taking SA-γmodel as the benchmark,the present ANN model is trained at two airfoils with various angles of attack,Mach numbers and Reynolds numbers,and tested with unseen airfoils in different flow *** a posteriori tests manifest that the mean pressure coefficient,skin friction coefficient,size of laminar separation bubble,mean streamwise velocity,Reynolds shear stress and lift/drag/moment coefficient from the present two-way coupling ANN model almost coincide with those from the benchmark SA-γ***,the ANN model proves to exhibit a higher calculation efficiency and better convergence quality than traditional SA-γmodel.

关键词： Transition Turbulence Eddy-viscosity model Artificial neural network Intermittency factor

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Collective stimulated Brillouin scattering modes of two crossing laser beams with shared scattered wave

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Matter and Radiation at Extremes 2021年第6期6卷 45-55页

作者： Jie Qiu Liang Hao Lihua Cao Shiyang Zou Institute of Applied Physics and Computational Mathematics Beijing 100094China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100871China

In inertial confinement fusion(ICF),overlapping of laser beams is *** to the effective high laser intensity of the overlapped beams,the collective mode of stimulated Brillouin scattering(SBS)with a shared scattered light wave is potentially *** this work,an exact analytic solution for the convective gain coefficient of the collective SBS modes with shared scattered wave is presented for two overlapped beams based on a linear *** effects of the crossing angle,polarization states,and finite beamoverlapping volume of the two laser beams on the shared light modes are analyzed for cases with zero and nonzero wavelength difference between the two *** is found that all these factors have a significant influence on the shared lightmodes of ***,the out-of-plane modes,in which the wavevectors of daughter waves lie in different planes from the two overlapped beams,are found to be important for certain polarization states and especially for obtuse crossing *** particular,adjusting the polarization directions of the two beams to be orthogonal to each other or tuning the wavelength difference to a sufficiently large value(of the order of nanometers)are found to be effective methods to suppress the shared light modes of *** work will be helpful for comprehending and suppressing collective SBS with shared scattered waves in ICF experiments.

关键词： polarization scattering tuning

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Simulation of the Weakly Nonlinear Rayleigh–Taylor Instability in Spherical Geometry

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Chinese physics Letters 2020年第5期37卷 73-76页

作者： Yun-Peng Yang Jing Zhang Zhi-Yuan Li Li-Feng Wang Jun-Feng Wu Wen-Hua Ye Xian-Tu He School of Physics Peking UniversityBeijing 100871 Center for Applied Physics and Technology HEDPSPeking UniversityBeijing 100871 Institute of Applied Physics and Computational Mathematics Bejing 100094

The Rayleigh-Taylor instability at the weakly nonlinear(WN)stage in spherical geometry is studied by numerical *** mode coupling processes are *** results are consistent with the WN model based on parameter expansion,while higher order effects are found to be *** Legendre mode perturbation Pn(cos B),the nonlinear saturation amplitude(NSA)of the fundamental mode decreases with the mode number *** n is large,the spherical NSA is lower than the corresponding planar ***,for large n,the planar NSA can be recovered by applying Fourier transformation to the bubble/spike near the equator and calculating the NSA of the converted trigonometric harmonic.

关键词： planar spherical negligible

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Coexistence of directed momentum current and ballistic energy diffusion in coupled non-Hermitian kicked rotors

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Physical Review A 2023年第3期107卷 032208-032208页

作者： Jian-Zheng Li Wen-Lei Zhao Jie Liu School of Science Jiangxi University of Science and Technology Ganzhou 341000 China Graduate School China Academy of Engineering Physics Beijing 100193 China HEDPS Center for Applied Physics and Technology and College of Engineering Peking University Beijing 100871 China

We numerically investigate the quantum transport in coupled kicked rotors with PT-symmetric potential. We find that spontaneous PT-symmetry breaking of wave functions emerges when the amplitude of the imaginary part of the complex potential is beyond a threshold value, which can be modulated by the coupling strength effectively. In the regime of PT-symmetry breaking, the particles driven by the periodical kicks move unidirectionally in momentum space, indicating the emergence of a directed current. Meanwhile, with increasing the coupling strength, we find a transition from the ballistic energy diffusion to a kind of modified ballistic energy diffusion where the width of the wave packet also increases with time in a power law. Our findings suggest that the decoherence effect induced by the interplay between the interparticle coupling and the non-Hermitian driving potential is responsible for these particular transport behaviors.

关键词： Diffusion Quantum chaos Non-Hermitean systems

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Determination of laser entrance hole size for ignition-scale octahedral spherical hohlraums

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Matter and Radiation at Extremes 2022年第6期7卷 41-49页

作者： Yao-Hua Chen Zhichao Li Hui Cao Kaiqiang Pan Sanwei Li Xufei Xie Bo Deng Qiangqiang Wang Zhurong Cao Lifei Hou Xingsen Che Pin Yang Yingjie Li Xiaoan He Tao Xu Yonggang Liu Yulong Li Xiangming Liu Haijun Zhang Wei Zhang Baibin Jiang Jun Xie Wei Zhou Xiaoxia Huang Wen Yi Huo Guoli Ren Kai Li Xudeng Hang Shu Li Chuanlei Zhai Jie Liu Shiyang Zou Yongkun Ding Ke Lan Institute of Applied Physics and Computational Mathematics Beijing 100094China Research Center of Laser Fusion China Academy of Engineering PhysicsMianyang 621900China Graduate School China Academy of Engineering PhysicsBeijingChina HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

A recently proposed octahedral spherical hohlraum with six laser entrance holes(LEHs)is an attractive concept for an upgraded laser facility aiming at a predictable and reproducible fusion gain with a simple target ***,with the laser energies available at present,LEH size can be a critical *** to the uncertainties in simulation results,the LEH size should be determined on the basis of experimental ***,determination of LEH size of an ignition target at a small-scale laser facility poses *** this paper,we propose to use the prepulse of an ignition pulse to determine the LEH size for ignition-scale hohlraums via LEH closure behavior,and we present convincing evidence from multiple diagnostics at the SGIII facility with ignition-scale hohlraum,laser prepulse,and laser beam *** LEH closure observed in our experiment is in agreement with data from the National Ignition *** total LEH area of the octahedral hohlraum is found to be very close to that of a cylindrical hohlraum,thus successfully demonstrating the feasibility of the octahedral hohlraum in terms of laser energy,which is crucially important for sizing an ignition-scale octahedrally configured laser *** work provides a novel way to determine the LEH size of an ignition target at a small-scale laser facility,and it can be applied to other hohlraum configurations for the indirect drive approach.

关键词： laser size spherical

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Vertical Alignment of Anisotropic Fillers Assisted by Expansion Flow in Polymer Composites

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Nano-Micro Letters 2022年第9期14卷 257-271页

作者： Hongyu Niu Haichang Guo Lei Kang Liucheng Ren Ruicong Lv Shulin Bai School of Materials Science and Engineering HEDPS/Center for Applied Physics and TechnologyKey Laboratory of Polymer Chemistry and Physics of Ministry of EducationPeking UniversityBeijing 100871People’s Republic of China Peking University Nanchang Innovation Institute 14#1‑2 FloorHigh‑level Talent Industrial ParkHigh‑Tech DistrictNanchang City 330224Jiangxi ProvincePeople’s Republic of China

Orientation control of anisotropic one-dimensional(1D)and two-dimensional(2D)materials in solutions is of great importance in many fields ranging from structural materials design,the thermal management,to energy *** fine control of vertical alignment of anisotropic fillers(such as graphene,boron nitride(BN),and carbon fiber)remains *** work presents a universal and scalable method for constructing vertically aligned structures of anisotropic fillers in composites assisted by the expansion flow(using2D BN platelets as a proof-of-concept).BN platelets in the silicone gel strip are oriented in a curved shape that includes vertical alignment in the central area and horizontal alignment close to strip *** to the vertical orientation of BN in the central area of strips,a throughplane thermal conductivity as high as 5.65 W m^(-1) K^(-1) was obtained,which can be further improved to 6.54 W m^(-1) K^(-1) by combining BN and pitch-based carbon *** expansion-flow-assisted alignment can be extended to the manufacture of a variety of polymer composites filled with 1D and 2D materials,which can find wide applications in batteries,electronics,and energy storage devices.

关键词： Boron nitride(BN) Silicone Expansion flow Vertical alignment Through-plane thermal conductivity

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Scaling laws of the out-of-time-order correlators at the transition to the spontaneous PT -symmetry breaking in a Floquet system

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Physical Review A 2023年第6期107卷 062201-062201页

作者： Wen-Lei Zhao Ru-Ru Wang Han Ke Jie Liu School of Science Jiangxi University of Science and Technology Ganzhou 341000 China Graduate School China Academy of Engineering Physics Beijing 100193 China HEDPS Center for Applied Physics and Technology and College of Engineering Peking University Beijing 100871 China

We investigate both numerically and analytically the dynamics of out-of-time-order correlators (OTOCs) in a non-Hermitian kicked rotor model, addressing the scaling laws of the time dependence of OTOCs at the transition to the spontaneous PT-symmetry breaking. In the unbroken phase of PT symmetry, the OTOCs increase monotonically and eventually saturate with time, demonstrating the freezing of information scrambling. Just beyond the phase transition points, the OTOCs increase in the power laws of time, with the exponent being larger than 2. Interestingly, the quadratic growth of OTOCs with time emerges when the system is far beyond the phase transition points. The above numerical findings are validated by our theoretical analysis, which provides a general framework with important implications for Floquet engineering and information scrambling in chaotic systems.

关键词： PT-symmetric quantum mechanics Quantum chaos

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