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Temperature dependence of migration features of self-interstitials in zirconium

Chinese Physics B 2017年第12期26卷 94-101页

作者：钟睿侯氢马超琼付宝勤汪俊 Key Laboratory for Radiation Physics and Technology Ministry of Education Institute of Nuclear Science and Technology Sichuan University Chengdu 610064 China

Molecular dynamics simulations are conducted to study self-interstitial migration in zirconium. By defining crystal lattice points where more than one atom is present in corresponding Wigner-Seitz cells, as the locations of self-interstitial atoms （LSIAs）, three types of events are identified as LSIA migrations：the jump remaining in one 〈1120〉 direction （ILJ）, the jump from one 〈1120〉 to another 〈1120〉 direction in the same basal plane （OLJ）, and the jump from one basal plane to an adjacent basal plane （OPJ）. The occurrence frequencies of the three types are calculated. ILJ is found to be a dominant event in a temperature range from 300 K to 1200 K, but the occurrence frequencies of OLJ and OPJ increase with temperature increasing. The total occurrence frequency of all jump types has a good linear dependence on temperature. Moreover, the migration trajectories of LSIAs in the hcp basal-plane is not what is observed if only conventional one-or two-dimensional migrations exists; rather, they exhibit the feature that we call fraction-dimensional. Using Monte Carlo simulations, the potential kinetic effects of fraction-dimensional migration, which is measured by the average number of lattice sites visited per jump event （denoted by nSPE）, are analysed. The significant differences between the nSPE value of the fraction-dimensional migration and those of conventional one-and two-dimensional migrations suggest that the conventional diffusion coefficient cannot give an accurate description of the underlying kinetics of SIAs in Zr. This conclusion could be generally meaningful for the cases where the low-dimensional migration of defects are observed.

关键词： molecular dynamics self-interstitial of zirconium anisotropic migration multiscale simulations

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multiscale SIMULATION OF INCIPIENT PLASTICITY AND DISLOCATION NUCLEATION ON NICKEL FILM DURING TILTED FLAT-ENDED NANOINDENTATION

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Acta Mechanica Solida Sinica 2015年第5期28卷 484-496页

作者： Fanlin Zeng Bing Zhao Yi Sun Department of Astronautic Science and Mechanics Harbin Institute of Technology

multiscale simulations of the tilted flat-ended nanoindentation with different tilted angles （from 5° ～ 30°） on the （-1 1 0） surface of nickel crystal were studied using the QC method. The model of the indentation is a flat-end indenter inclined by an angle ε driven into a half- plane vertically. Load-displacement responses, initiM stages of the plasticity deformations and dislocation emissions for nickel film at different inclined angles were obtained and analyzed as well. An energy criterion was successfully proposed to analyze the critical load for the first dislocation emission beneath the edge of the indenter. Simulation results agree well with analytical ones. An elastic model based on the contact theory and the Peierls-Nabarro dislocation model were combined to analyze when and where the dislocation will be emitted beneath the lower surface of an inclined indenter. Results indicate that the key parameter is the ratio of the contact half- width to the position of the slip plane. This parameter shows the range in which a dislocation will probably be emitted. This mechanism explains the simulation results well. This work is of value for understanding the mechanism of dislocation emissions of FCC crystals under tilted flat- ended nanoindentation while providing approaches to predicting when the first dislocation will be emitted and where subsequent dislocations will probably be emitted.

关键词： multiscale simulations tilted flat-ended nanoindentation dislocations mechanism

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Electric field induced magnetization reversal in magnet/insulator nanoheterostructure

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International Journal of Smart and Nano Materials 2020年第3期11卷 298-309页

作者： Qihua Gong Min Yi Bai-Xiang Xu Institute of Materials Science Technische Universität DarmstadtDarmstadtGermany State Key Lab of Mechanics and Control of Mechanical Structures&Key Lab for Intelligent Nano Materials and Devices of Ministry of Education&College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics(NUAA)NanjingChina

Electric-field control of magnetization reversal is promising for lowpower *** in a magnet/insulator nanoheterostructure which is the fundamental unit of magnetic tunneling junction in spintronics,we demonstrate the electric field induced 180°magne-tization switching through a multiscale study combining firstprinciples calculations and finite-temperature magnetization *** the model nanoheterostructure MgO/Fe/Cu with insu-lator MgO,soft nanomagnet Fe and capping layer Cu,through firstprinciples calculations we find its magnetocrystalline anisotropy linearly varying with the electric *** finite-temperature magnetization dynamics which is informed by the first-principles results,we disclose that a room-temperature 180°magnetization switching with switching probability higher than 90%is achievable by controlling the electric-field pulse and the nanoheterostructure *** 180°switching could be fast realized within 5 *** study is useful for the design of low-power,fast,and miniaturized nanoscale electric-field-controlled spintronics.

关键词： Magnetization reversal nanoheterostructure electric field spintronics multiscale simulations switching probability

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A Macro Projective IntegrationMethod in 2D Microscopic System Applied to Nonlinear Ion Acoustic Waves in a Plasma

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Communications in Computational Physics 2008年第8期4卷 556-574页

作者： A.M.Maluckov S.Ishiguro M.M.Skoric National Institute for Fusion Science Toki509-5292Japan Faculty of Science University of Niˇs18001Serbia

In the Equation-free framework,amacro-coarse projective integrationmethod consists of two parts:the time stepper and time projection on macro *** first one consists of lifting,micro simulation and *** extracting directly from microscopic simulations the information which would be obtained from the macroscopic model of two-dimensional microscopic systems,the time stepper based on the one-dimensional cumulative distribution functions,the marginal cumulative and appropriate number of the conditional cumulative distributions,is *** this procedure is tested on the nonlinear ion acoustic wave in a *** numerical micro-solver is the one dimensional electrostatic particle-in-cell *** is shown that particle correlations related to wave structures are better preserved by the new *** lifting step is critically related to the noise in *** enlarged noise,rise of correlations,trapping of particles during the wave steepening can seriously violate the basic assumptions of the equation-free approach.

关键词： multiscale simulations E-free framework nonlinear plasmas

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