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采用基于壳模型的分子动力学模拟方法, 研究了存在外延压应变时BaTiO3铁电体的辐射位移效应, 以O原子作为初冲原子(primary knock-on atom, PKA), 能量为1 keV, 方向为[001], 分别计算了外延压应变为0, 0.4%, 0.8%, 1.2%, 1.6%, 2.0%时体系的缺陷数量、分布, 以及辐射前后的极化强度, 比较了压应变为2%以及无应变下损伤区域、缺陷离位距离和反向外电场下PKA的迁移距离. 结果表明, 随外延压应变增加体系极化近似线性增加, 辐射后极化降低幅度降低、缺陷产生的数量有所减小, 2% 压应变存在时缺陷原子的离位距离、PKA在反向外电场作用下的迁移距离和损伤区域都小于无应变的情况, 说明外延压应变的存在对辐射造成的晶格损伤具有抑制作用, 对辐射损伤具有改善作用, 可以通过引入外延压应变来调控BaTiO3的辐射损伤.
关键词:
应变
3')" href="#">BaTiO3
辐射损伤
分子动力学模拟 相似文献
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采用基于壳模型的分子动力学模拟方法,研究了存在外延压应变时BaTiO3铁电体的辐射位移效应,以O原子作为初冲原子(primary knock-on atom,PKA),能量为1 keV,方向为[001],分别计算了外延压应变为0,0.4%,0.8%,1.2%,1.6%,2.0%时体系的缺陷数量、分布,以及辐射前后的极化强度,比较了压应变为2%以及无应变下损伤区域、缺陷离位距离和反向外电场下PKA的迁移距离.结果表明,随外延压应变增加体系极化近似线性增加,辐射后极化降低幅度降低、缺陷产生的数量有所减小,2%压应变存在时缺陷原子的离位距离、PKA在反向外电场作用下的迁移距离和损伤区域都小于无应变的情况,说明外延压应变的存在对辐射造成的晶格损伤具有抑制作用,对辐射损伤具有改善作用,可以通过引入外延压应变来调控BaTiO3的辐射损伤. 相似文献
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基于密度泛函理论框架下的第一性原理计算方法,系统的研究了碱金属Rb原子修饰具有空位缺陷h-BN单层体系的储氢性能.发现Rb原子可稳定吸附在h-BN单层的B单空位缺陷(VB)上,且Rb原子间无团簇倾向,单个Rb原子最多可稳定吸附5个H2分子,H2分子平均吸附能在0.18-0.21 eV范围内.电子结构分析表明H2分子主要通过极化机制和轨道杂化作用吸附在Rb修饰的缺陷h-BN单层体系上.Rb双侧修饰缺陷h-BN单层体系的理论储氢质量比可以达到5.0 wt%.基于范特霍夫方程和从头算分子动力学(AIMD)模拟对储氢体系的热力学稳定性进行了进一步的研究. 相似文献
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本文先应用分子动力学模拟BaTiO3体系在初级击出原子(primary knock-on atom, PKA)轰击下缺陷产生和复合的动力学过程, 模拟结果表明:PKA的方向和能量对缺陷数目有重要影响, 并计算了Ba, O和Ti原子的平均位移阈能分别为69 eV, 51 eV和123 eV, 远大于SRIM程序默认的位移阈能25 eV. 然后应用蒙特卡罗软件包SRIM, 模拟质子在BaTiO3薄膜中的能量损失过程, 比较位移阈能对模拟结果的影响, 分析质子能量和入射角度对空位数量以及分布的影响. 结果表明空位数量随着质子能量增加而增加, 增加的速率随能量的增加是降低的;当入射角度大于60°, 空位数量随入射角增大而明显减少. 相似文献
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采用TLHT势和经典分子动力学方法研究了稀有气体原子(He,Ne,Ar,Kr,Xe)进入带缺陷的单壁纳米碳管(SWCNT)的动力学过程,计算出了稀有气体原子分别从管壁和管口入射时,它们能封装在SWCNT中的能量阈值Ek0,并与理想结构情形做了比较.结果表明:随着管壁缺陷半径r的增加,Ek0减小;当r<4.5 ?时,给定合适的初始动能,稀有气体原子能封装在纳米碳管中;而r=4.5 ?时,稀有气体原子不能封装在碳管中,且此时缺陷对Ar,Kr和Xe的输运特性有很大影响.
关键词:
纳米碳管
缺陷
稀有气体原子
分子动力学模拟 相似文献
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锆钛酸铅镧(Pb0.94La0.06Zr0.96Ti0.04O3,PLZT)具有良好的介电和储能性质,是高效、高能量密度电容元件和存储器件的基体材料.为研究该材料的中子辐照损伤,首先基于Geant4程序包模拟了能量为1—14 MeV中子辐照浩钛酸铅镧(PLZT)材料产生的反冲原子能谱,然后根据产生的反冲原子种类和最大能量,利用二元碰撞方法模拟了不同能量的离子在PLZT中产生的位移损伤(包括空位和间隙原子),最后根据反冲原子能谱和对应能量离子在材料中产生的缺陷数目计算了不同能量的中子在PLZT材料中产生缺陷浓度以及分布.结果发现,对于1—14 MeV能区的快中子而言,其在厚度为3 cm的PLZT材料中产生的缺陷数目近似与中子能量无关,约为460±120空位/中子.辐照损伤在3cm厚度内随深度的增加而略有减小,总体变化小于50%,该减小主要是由于中子的反散射导致.本工作为计算中子在材料中的位移损伤提供了一种方法,同时模拟结果可为研究PLZT基电子器件的中子辐照效应提供指导. 相似文献
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We report on the results of computer simulation of point defect production near voids in crystalline Cu at primary knock-on atom (PKA) kinetic energies ranging from 5 to 1000?eV. The PKA energy dependence of numbers of created defects are revealed. The threshold energy for a stable vacancy formation is found to be much smaller than that for an interstitial atom, which results in a biased formation of vacancies in the void proximity in the whole investigated range of PKA energies. Dissolution of small voids by subthreshold irradiation is simulated. The impact of considered radiation effects on kinetics of radiation damage is discussed. 相似文献
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Large-scale molecular dynamics of cascade production of the primary damage state are performed in fcc nanocrystalline Ni of average grain diameters of 5 and 12 nm. Primary knock-on atom kinetic energies of 5-30 keV are simulated. During the thermal spike phase, significant atomic motion towards the surrounding grain boundary structure is observed, characterized by many replacement-collision sequences. Upon resolidification, the excess volume condenses to form vacancy dominated defects with a complex partial dislocation network forming at higher energies. 相似文献
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采用60Coγ射线辐照纯净的多壁碳纳米管,用高分辨透射电镜和拉曼光谱,研究了多壁碳纳米管由石墨结构向无定形结构转变的演化过程.发现在γ射线辐照下,碳纳米管的外部石墨层逐渐失去最初的有序结构而向无定形结构转变.而且,随着γ射线辐照剂量的增加,无定形结构不断推进,而石墨层结构则不断减小,直至使整个碳纳米管变为一个中空的无定形纳米线结构.用原子位移理论和溅射机理对这种转变过程进行了分析.γ射线轰击碳纳米管击出碳原子,碳原子停留在晶格的间隙位置上产生间隙原子,在它原来的平衡位置则留下一个空位.当轰击粒子动能足够大时导致碰撞级联效应,无序结构增加.多数空位和间隙原子可能相互复合而彼此退火,但仍有少数原子作为间隙原子而造成晶格进一步缺陷.辐射也可以引起碳原子的溅射,溅射出来的碳原子沉积在碳纳米管的外壁上形成一层无定形碳结构. 相似文献
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We propose several simple models to study the physical origin and respective importance in surface analysis of different mechanisms of enhanced atomic mobility in sputtered samples, and their influence on the depth resolution of the analysis. We study successively the effects of point defects created by the irradiation, collision cascades (effects of atomic displacements and also thermal spikes) and knock-on. The enhanced diffusion due to point defects is shown to be dominant in low melting point elements where vacancies are mobile. In other systems where vacancies are not mobile during analysis the effect of knock-on by primary ions is shown to be the most important. 相似文献
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A. V. Korchuganov K. P. Zolnikov D. S. Kryzhevich V. M. Chernov S. G. Psakhie 《Physics of Atomic Nuclei》2016,79(7):1193-1198
The investigation of plastic deformation nucleation in metals and alloys under irradiation and mechanical loading is one of the topical issues of materials science. Specific features of nucleation and evolution of the defect system in stressed and irradiated iron, vanadium, and copper crystallites were studied by molecular dynamics simulation. Mechanical loading was performed in such a way that the modeled crystallite volume remained unchanged. The energy of the primary knock-on atom initiating a cascade of atomic displacements in a stressed crystallite was varied from 0.05 to 50 keV. It was found that atomic displacement cascades might cause global structural transformations in a region far larger than the radiation-damaged area. These changes are similar to the ones occurring in the process of mechanical loading of samples. They are implemented by twinning (in iron and vanadium) or through the formation of partial dislocation loops (in copper). 相似文献
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Using perturbed angular correlations of γ rays the behaviour of Frenkel defects in n-type germanium is studied.111In/111Cd probes either serve as primary knock-on atoms in the production of Frenkel defects by neutrino recoil or as trapping agents
for defects produced by electron irradiation. The neutrino recoil process leads to a defect which is characterized by vQ=e2qQ/h=42(2) MHz (η=0.6), while a defect with vQ=423(1) MHz (η=0) is observed after electron irradiation and thermal annealing. 相似文献