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Structure of self-interstitial atom clusters in iron and copper

机译：铁和铜中自填原子簇的结构

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The dislocation core structure of self-interstitial atom (SIA) clusters in bcc iron and fcc copper is determined using the hybrid ab initio continuum method of Banerjee et al. [Philos. Mag. 87, 4131 (2007)]. To reduce reliance on empirical potentials and to facilitate predictions of the effects of local chemistry and stress on the structure of defects, we present here a hybrid extension of the Peierls-Nabarro continuum model, with lattice resistance to slip determined separately from ab initio calculations. A method is developed to reconstruct atomic arrangements and geometry of SIA clusters from the hybrid model. The results are shown to compare well with molecular-dynamics simulations. In iron, the core structure does not show dependence on the size of the self-interstitial cluster, and is nearly identical to that of a straight edge dislocation. However, the core structure of SIA clusters in Cu is shown to depend strongly on the cluster size. Small SIA clusters are found to have nondissociated compact dislocation cores, with a strong merging of Shockley partial dislocations and a relatively narrow stacking fault (SF) region. The compact nature of the SIA core in copper is attributed to the strong dependence of the self-energy on the cluster size. As the number of atoms in the SIA cluster increases, Shockley partial dislocations separate and the SF region widens, rendering the SIA core structure to that of an edge dislocation. The separation distance between the two partials widens as the cluster size increases, and tends to the value of a straight edge dislocation for cluster sizes above 400 atoms. The local stress is found to have a significant effect on the atomic arrangements within SIA clusters in copper and the width of the stacking faults. An applied external shear can delocalize the core of an SIA cluster in copper, with positive shear defined to be on the (111) plane along the [112] direction. For an SIA cluster containing 1600 atoms, a positive 1 GPa shear stress delocalizes the cluster and expands the SF to 30b, while a negative shear stress of 2 GPa contracts the core to less than 5b, where b is the Burgers vector magnitude.
机译：bcc铁和fcc铜中自填隙原子（SIA）团簇的位错核心结构是使用Banerjee等人的混合从头算连续性方法确定的。 [菲洛斯。魔术师87，4131（2007）]。为了减少对经验电势的依赖，并促进对局部化学和应力对缺陷结构的影响的预测，我们在此介绍Peierls-Nabarro连续体模型的混合扩展，并从头算计算中分别确定滑移的晶格阻力。开发了一种从混合模型重建SIA团簇的原子排列和几何形状的方法。结果表明，与分子动力学模拟可以很好地进行比较。在铁中，核心结构不依赖于自填隙簇的大小，与直边位错几乎相同。但是，显示出Cu中SIA簇的核心结构在很大程度上取决于簇的大小。发现小型SIA团簇具有未分离的致密位错核心，具有肖克利部分位错的强烈合并和相对较窄的堆叠断层（SF）区域。 SIA芯在铜中的紧凑特性归因于自能量对簇尺寸的强烈依赖。随着SIA簇中原子数的增加，肖克利局部位错分离并且SF区变宽，从而使SIA核心结构变为边缘位错。随着团簇尺寸的增加，两个部分之间的分隔距离变宽，并且对于超过400个原子的团簇尺寸，趋向于直边位错的值。发现局部应力对铜的SIA簇中的原子排列以及堆垛层错的宽度有重要影响。施加的外部剪切力可以使SIA簇的核心在铜中偏心，而正向剪切力定义为沿[112]方向在（111）平面上。对于包含1600个原子的SIA团簇，正的1 GPa剪应力使团簇离域并使SF扩展至30b，而2 GPa的负剪应力使核心收缩至小于5b，其中b是Burgers矢量量级。

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