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首页> 外文期刊>Journal of the Mechanics and Physics of Solids >Electronic structure study of screw dislocation core energetics in Aluminum and core energetics informed forces in a dislocation aggregate
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Electronic structure study of screw dislocation core energetics in Aluminum and core energetics informed forces in a dislocation aggregate

机译：铝中螺旋位错核心能量学和位错集合体中核心能量知情力的电子结构研究

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摘要

We use a real-space formulation of orbital-free DFT to study the core energetics and core structure of an isolated screw dislocation in Aluminum. Using a direct energetics based approach, we estimate the core size of a perfect screw dislocation to be ≈ 7 |b|, which is considerably larger than previous estimates of 1-3 |b| based on displacement fields. The perfect screw upon structural relaxation dissociates into two Shockley partials with partial separation distances of 8.2 Å and 6.6 Å  measured from the screw and edge component differential displacement plots, respectively. Similar to a previous electronic structure study on edge dislocation, we find that the core energy of the relaxed screw dislocation is not a constant, but strongly dependent on macroscopic deformations. Next, we use the edge and screw dislocation core energetics data with physically reasonable assumptions to develop a continuum energetics model for an aggregate of dislocations that accounts for the core energy dependence on macroscopic deformations. Further, we use this energetics model in a discrete dislocation network, and from the variations of the core energy with respect to the nodal positions of the network, we obtain the nodal core force which can directly be incorporated into discrete dislocation dynamics frameworks. We analyze and classify the nodal core force into three different contributions based on their decay behavior. Two of these contributions to the core force, both arising from the core energy dependence on macroscopic deformations, are not accounted for in currently used discrete dislocation dynamics models which assume the core energy to be a constant excepting for its dependence on the dislocation line orientation. Using case studies involving simple dislocation structures, we demonstrate that the contribution to the core force from the core energy dependence on macroscopic deformations can be significant in comparison to the elastic Peach-Koehler force even up to distances of 10-15 nm between dislocation structures. Thus, these core effects, whose origins are in the electronic structure of the dislocation core, can play an important role in influencing dislocation-dislocation interactions to much larger distances than considered heretofore.
机译：我们使用无轨道DFT的实空间公式来研究铝中孤立的螺旋位错的核心能量和核心结构。使用基于直接能量学的方法，我们估计理想螺钉位错的核心尺寸约为≈7 | b |，这比先前的1-3 | b |估计要大得多。基于位移场。结构松动时的理想螺钉分解为两个Shockley子部件，分别从螺钉和边缘组件差分位移图测得的局部分离距离为8.2Å和6.6Å。与先前关于边缘错位的电子结构研究相似，我们发现松弛的螺钉错位的核心能量不是恒定的，而是强烈依赖于宏观变形。接下来，我们使用具有物理上合理假设的边角螺钉位错核心高能数据，为位错聚集体建立了一个连续的能量学模型，该模型解释了核心能量对宏观变形的依赖性。此外，我们在离散位错网络中使用这种能量学模型，从核心能量相对于网络节点位置的变化中，我们获得了节点核心力，可以直接将其纳入离散位错动力学框架中。我们基于节点的衰变行为将节点核心力分析和分类为三个不同的贡献。在当前使用的离散位错动力学模型中，这两个对核心力的贡献都是由于核心能量对宏观变形的依赖性而产生的，该模型假设核心能量除依赖于位错线的方向而为常数外，都为常数。通过使用涉及简单位错结构的案例研究，我们证明，即使位错结构之间的距离达到10-15 nm，与宏观的形变相比，核心能量对宏观形变的依赖性对核心力的贡献也很重要。因此，这些核心效应的起源是位错核心的电子结构，在将位错-位错相互作用影响到比迄今为止所考虑的大得多的距离时，可以发挥重要作用。

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  • 来源
    《Journal of the Mechanics and Physics of Solids》 |2017年第7期|115-143|共29页
  • 作者

    Das Sambit K.; Gavini Vikram;

  • 作者单位

    Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, United States;

    Department of Mechanical Engineering, Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, United States;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
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