检索结果-内蒙古大学图书馆

Ab initio validation on the connection between atomistic and hydrodynamic description to unravel the ion dynamics of warm dense matter

学校读者我要写书评

暂无评论

Physical Review Research 2021年第3期3卷 033116-033116页

作者： Qiyu Zeng Xiaoxiang Yu Yunpeng Yao Tianyu Gao Bo Chen Shen Zhang Dongdong Kang Han Wang Jiayu Dai Department of Physics National University of Defense Technology Changsha Hunan 410073 People's Republic of China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 People's Republic of China

Ion dynamics exhibits inherent multiscale characteristics because it contains both atomistic and hydrodynamic behaviors. Although atomic-scale ab initio molecular dynamics is the subject of intense research on warm dense matter, the macroscopic relaxation process contained in the zero-frequency mode of the ionic dynamic structure factor (DSF) cannot be demonstrated due to the limitation of simulation sizes. Here, we fill this gap via the machine-learning deep potential method. To capture the ion dynamics near the hydrodynamic limit with ab initio accuracy, an accurate and efficient electron-temperature-dependent interatomic potential was constructed. We quantitatively verify the consistency of thermal diffusivities obtained from hydrodynamics and the fluctuation-dissipation theorem and further provide a microscopic perspective of energy transport to understand the zero-frequency mode of DSF. As implemented in two temperature states, a competitive mechanism is found to account for the damping of the zero-frequency mode.

关键词： High-energy-density plasmas Warm-dense matter Molecular dynamics

Hole Statistics of Equilibrium 2D and 3D Hard-Sphere Crystals

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Wang, Haina Huse, David A. Torquato, Salvatore Department of Chemistry Princeton University PrincetonNJ08544 United States Department of Physics Princeton University PrincetonNJ08544 United States Department of Chemistry Department of Physics Princeton Institute of Materials and Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States

The probability of finding a spherical "hole" of a given radius r contains crucial structural information about many-body systems. Such hole statistics, including the void conditional nearest-neighbor probability functions GV (r), have been well studied for hard-sphere fluids in d-dimensional Euclidean space Rd. However, little is known about these functions for hard-sphere crystals for values of r beyond the hard-sphere diameter, as large holes are extremely rare in crystal phases. To overcome these computational challenges, we introduce a biased-sampling scheme that accurately determines hole statistics for equilibrium hard spheres on ranges of r that far extend those that could be previously explored. We discover that GV (r) in crystal and hexatic states exhibits oscillations whose amplitudes increase rapidly with the packing fraction, which stands in contrast to GV (r) for fluid states that is monotonic in r. The oscillations in GV (r) for 2D crystals are strongly correlated with the local orientational order metric in the vicinity of the holes, and variations in GV (r) for 3D states indicate a transition between tetrahedral and octahedral holes, demonstrating the power of GV (r) as a probe of local coordination geometry. To further study the statistics of interparticle spacing in hard-sphere systems, we compute the local packing fraction distribution f(l) of Delaunay cells, and find that for d ≤ 3, the excess kurtosis of f(l) switches sign at a certain transitional global packing fraction. Our investigation facilitates the study of structural and bulk properties of materials that involve the creation of rare large holes, such as the solubility of alloys. © 2024, CC BY.

关键词： Spheres

The decays of the fully open flavor state (Equation presented) in a D∗K∗ molecule scenario

学校读者我要写书评

暂无评论

arXiv 2022年

作者： Yue, Zi-Li Xiao, Cheng-Jian Chen, Dian-Yong School of Physics Southeast University Nanjing210094 China Institute of Applied Physics and Computational Mathematics Beijing100088 China Lanzhou Center for Theoretical Physics Lanzhou University Lanzhou730000 China

Inspired by the recent observations of (Equation presented) in the the processes (Equation presented) and (Equation presented) by LHCb Collaboration, we investigate the decay properties of the (Equation presented) in a D∗K∗ molecule scenario, and the widths of (Equation presented), D+s π−, D∗s+ρ−, D(')+s1π−, and D∗0(Dπ)0 are estimated. Our estimations indicate that the width of (Equation presented) is sizable to be observed and the dominant decay mode of (Equation presented). Considering the isospin symmetry, we proposed to search (Equation presented) in the D+K+ invariant mass distributions of the process B+ → D+D−K+, where some preliminary experimental hints have been observed by LHCb Collaboration. © 2022, CC BY.

关键词： Molecules

Interlayer electric multipoles induced by in-plane field from quantum geometric origins

学校读者我要写书评

暂无评论

arXiv 2023年

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

We show that interlayer charge transfer in 2D materials can be driven by an in-plane electric field, giving rise to electrical multipole generation in linear and second order of in-plane field. The linear and nonlinear effects have quantum geometric origins in the Berry curvature and quantum metric respectively, defined in extended parameter spaces characteristic of layered materials. We elucidate their symmetry characters, and demonstrate sizable dipole and quadrupole polarizations respectively in twisted bilayers and trilayers of transition metal dichalcogenides. Furthermore, we show that the effect is strongly enhanced during the topological phase transition tuned by interlayer translation. The effects point to a new electric control on layer quantum degree of freedom. Copyright © 2023, The Authors. All rights reserved.

关键词： Nanocrystals

Large-scale Kinetic Simulations of Colliding Plasmas within a Hohlraum of Indirect Drive Inertial Confinement Fusions

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Liang, Tianyi Wu, Dong Ning, Xiaochuan Shan, Lianqiang Yuan, Zongqiang Cai, Hongbo Sheng, Zhengmao He, Xiantu Institute for Fusion Theory and Simulation School of Physics Zhejiang University Hangzhou310058 China Key Laboratory for Laser Plasmas School of Physics and Astronomy Collaborative Innovation Center of IFSA Shanghai Jiao Tong University Shanghai200240 China Science and Technology on Plasma Physics Laboratory Research Center of Laser Fusion CAEP Mianyang621900 China Institute of Applied Physics and Computational Mathematics CAEP Beijing100094 China

The National Ignition Facility has recently achieved successful burning plasma and ignition using the inertial confinement fusion (ICF) approach. However, there are still many fundamental physics phenomena that are not well understood, including the kinetic processes in the hohlraum. Shan et al. [Phys. Rev. Lett, 120, 195001, 2018] utilized the energy spectra of neutrons to investigate the kinetic colliding plasma in a hohlraum of indirect drive ICF. However, due to the typical large spatial-temporal scales, this experiment could not be well simulated by using available codes at that time. Utilizing our advanced high-order implicit PIC code, LAPINS, we were able to successfully reproduce the experiment on a large scale of both spatial and temporal dimensions, in which the original computational scale was increased by approximately 7 to 8 orders of magnitude. When gold plasmas expand into deuterium plasmas, a kinetic shock is generated and propagates within deuterium plasmas. Simulations allow us to observe the entire progression of a strong shock wave, including its initial formation and steady propagation. Although both electrons and gold ions are collisional (on a small scale compared to the shock wave), deuterium ions seem to be collisionless. This is because a quasi-monoenergetic spectrum of deuterium ions can be generated by reflecting ions from the shock front, which then leads to the production of neutrons with unusual broadening due to beam-target nuclear reactions. This work displays an unprecedented kinetic analysis of an existing experiment, shedding light on the mechanisms behind shock wave formation. It also serves as a reference for benchmark simulations of upcoming new simulation codes and may be relevant for future research on mixtures and entropy increments at plasma interfaces. © 2023, CC BY.

关键词： Inertial confinement fusion

Nearly-optimal state preparation for quantum simulations of lattice gauge theories

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Kane, Christopher F. Gomes, Niladri Kreshchuk, Michael Department of Physics University of Arizona TucsonAZ85719 United States Applied Mathematics and Computational Research Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Physics Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States

We present several improvements to the recently developed ground state preparation algorithm based on the Quantum Eigenvalue Transformation for Unitary Matrices (QETU), apply this algorithm to a lattice formulation of U(1) gauge theory in 2+1D, as well as propose a novel application of QETU, a highly efficient preparation of Gaussian distributions. The QETU technique has been originally proposed as an algorithm for nearly-optimal ground state preparation and ground state energy estimation on early fault-tolerant devices. It uses the time-evolution input model, which can potentially overcome the large overall prefactor in the asymptotic gate cost arising in similar algorithms based on the Hamiltonian input model. We present modifications to the original QETU algorithm that significantly reduce the cost for the cases of both exact and Trotterized implementation of the time evolution circuit. We use QETU to prepare the ground state of a U(1) lattice gauge theory in 2 spatial dimensions, explore the dependence of computational resources on the desired precision and system parameters, and discuss the applicability of our results to general lattice gauge theories. We also demonstrate how the QETU technique can be utilized for preparing Gaussian distributions and wave packets in a way which outperforms existing algorithms for as little as nq 2 − 5 qubits. © 2023, CC BY.

关键词： Ground state

Measurement of Time-Dependent Drive Flux on the Capsule for Indirectly Driven Inertial Confinement Fusion Experiments

学校读者我要写书评

暂无评论

Physical Review Letters 2022年第7期128卷 075001-075001页

作者： Xufei Xie Lifei Hou Hongbo Cai Changshu Wu Xiaoshi Peng Xiaoxi Duan Shenye Liu Dong Yang Sanwei Li Zhichao Li Qi Li Yonggang Liu Huabin Du Kuan Ren Fengjun Ge Weiming Yang Liang Guo Wanli Shang Xingsen Che Longfei Jing Yulong Li Huiyue Wei Yimeng Yang Ao Sun Ruizhen Yu Yunbao Huang Xiaohua Jiang Tao Xu Xiaoan He Chaoguang Li Yingjie Li Feng Wang Haien He Jiamin Yang Kai Du Shaoen Jiang Baohan Zhang Yongkun Ding Laser fusion Research Center Chinese Academy of Engineering Physics Mianyang 621900 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China Center for Applied Physics and Technology HEDPS and College of Engineering Peking University Beijing 100871 China Mechatronics School of Guangdong University of Technology Guangzhou 510080 China

A new method for measuring the time-dependent drive flux at the hohlraum center is proposed as a better alternative to conventional wall-based techniques. The drive flux here is obtained by simultaneous measurement of the reemitted flux and shock velocity from a three-layered “cakelike” sample. With these two independent observables, the influence induced by the uncertainty of the material parameters of the sample can be effectively decreased. The influence from the closure of the laser entrance hole, which was the main challenge in conventional wall-based techniques, was avoided through localized reemitted flux measurement, facilitating drive flux measurement throughout the entire time history. These studies pave a new way for probing the time-dependent drive flux, for both cylindrical hohlraums and novel hohlraums with six laser entrance holes.

关键词： Inertial confinement fusion Laser inertial confinement X-ray & gamma ray plasma measurements

Ab initio multi-scale modeling of ferroelectrics: The case of PbTiO3

学校读者我要写书评

暂无评论

arXiv 2022年

作者： Xie, Pinchen Chen, Yixiao Weinan, E. Car, Roberto Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States Department of Mathematics and Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States Department of Chemistry Department of Physics Program in Applied and Computational Mathematics Princeton Institute for the Science and Technology of Materials Princeton University PrincetonNJ08544 United States

We report an ab initio multi-scale study of lead titanate using the Deep Potential (DP) models, a family of machine learning-based atomistic models, trained on first-principles density functional theory data, to represent potential and polarization surfaces. Our approach includes anharmonic effects beyond the limitations of reduced models and of the linear approximation for the polarization. The calculated enthalpy, spontaneous polarization, specific heat and dielectric susceptibility agree well with experiments on single crystals. In addition, we study how the free energy depends on the polarization with enhanced sampling methods, further supporting the first-order and order-disorder character of the transition. The latter is evidenced by persistence of local dipoles above the transition temperature. The simulated free energy surface as a function of the global polarization leads to a Landau-Devonshire theory of the single domain crystal. © 2022, CC BY.

关键词： Free energy

Theoretical evidence of H-He demixing under Jupiter and Saturn conditions

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Chang, Xiaoju Chen, Bo Zeng, Qiyu Wang, Han Chen, Kaiguo Tong, Qunchao Yu, Xiaoxiang Kang, Dongdong Zhang, Shen Guo, Fangyu Hou, Yong Zhao, Zengxiu Yao, Yansun Ma, Yanming Dai, Jiayu College of Science National University of Defense Technology Changsha410073 China Hunan Key Laboratory of Extreme Matter and Applications National University of Defense Technology Changsha410073 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China Department of Physics and Engineering Physics University of Saskatchewan SaskatoonSKS7N 5E2 Canada State Key Lab of Superhard Materials International Center for Computational Method and Software College of Physics Jilin University Changchun130012 China International Center of Future Science Jilin University Changchun130012 China

The immiscibility of hydrogen-helium mixture under the temperature and pressure conditions of planetary interiors is crucial for understanding the structures of gas giant planets (e.g., Jupiter and Saturn). While the experimental probe at such extreme conditions is challenging, theoretical simulation is heavily relied in an effort to unravel the mixing behavior of hydrogen and helium. Here we develop a method via a machine learning accelerated molecular dynamics simulation to quantify the physical separation of hydrogen and helium under the conditions of planetary interiors. The immiscibility line achieved with the developed method yields substantially higher demixing temperatures at pressure above 1.5 Mbar than earlier theoretical data, but matches better to the experimental estimate. Our results suggest a possibility that H-He demixing takes place in a large fraction of the interior radii of Jupiter and Saturn, i.e., 27.5% in Jupiter and 48.3% in Saturn. This indication of an H-He immiscible layer hints at the formation of helium rain and offers a potential explanation for the decrease of helium in the atmospheres of Jupiter and Saturn. © 2023, CC BY.

关键词： Planets