The structures of pyramidal-II $〈c+a〉$ dislocations, one of the most important defects in structural hexagonal-close-packed (HCP) metals, have not been fully characterized for many of the HCP metals in use today. Here, we employ ab initio informed phase-field dislocation dynamics to determine the minimum energy structure of pyramidal $\left\{\overline{1}\overline{1}22\right\}〈11\overline{2}3〉$ dislocations in ten HCP metals, including Be, Co, Mg, Re, Ti, Zn, Cd, Hf, Y, and Zr. As input for the simulations, we calculate, using first-principles density functional theory, the $\left\{\overline{1}\overline{1}22\right\}$ generalized stacking fault energy (GSFE) curves for all ten metals. From these calculations, it is found that magnetism in Co is necessary for achieving a local minimum in the GSFE curve. We observe in simulations that edge and screw character dislocations split into two partials separated by a low-energy intrinsic stacking fault. The splitting distance is shown to scale inversely with the local minimum energy normalized by the product of its shear modulus and Burgers vector. Interestingly, some HCP metals exhibit an asymmetric structure, with either unequal partial Burgers vectors or widths, in contrast to the symmetric configuration expected from linear elastic dislocation theory. We explain these structures by properties of the local maxima in their GSFE curves. Metals with larger degrees of elastic anisotropy result in dislocations with larger splitting distances than would be expected under the commonly used assumption of elastic isotropy. These findings on the sizes and asymmetry in the structures of pyramidal-II $〈c+a〉$ dislocations are fundamental to understanding how these dislocations glide and interact or react with other defects when these metals are mechanically strained.

中文翻译：

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十种六方密堆积金属中锥体II <c + a>位错的不对称平衡核心结构

金字塔II的结构 $〈C+\mathrm{一个}〉$位错是结构六方密堆积（HCP）金属中最重要的缺陷之一，对于当今使用的许多HCP金属而言，位错尚未得到充分表征。在这里，我们采用从头算的相场错位动力学来确定金字塔形的最小能量结构$\left\{\overline{\mathrm{1个}}\overline{\mathrm{1个}}\mathrm{2个}\mathrm{2个}\right\}〈11\overline{\mathrm{2个}}3〉$十种HCP金属中的位错，包括Be，Co，Mg，Re，Ti，Zn，Cd，Hf，Y和Zr。作为模拟的输入，我们使用第一原理密度泛函理论来计算$\left\{\overline{\mathrm{1个}}\overline{\mathrm{1个}}\mathrm{2个}\mathrm{2个}\right\}$所有十种金属的广义堆垛层错能（GSFE）曲线。从这些计算中发现，Co中的磁性对于在GSFE曲线中达到局部最小值是必要的。我们在仿真中观察到，边缘和螺钉的位错被低能的固有堆垛层错分成两个部分。示出分裂距离与通过其剪切模量和Burgers矢量的乘积归一化的局部最小能量成反比。有趣的是，与线性弹性位错理论所期望的对称构型相反，某些HCP金属表现出不对称的结构，具有不相等的部分Burgers向量或宽度。我们通过GSFE曲线中局部最大值的特性来解释这些结构。弹性各向异性程度较高的金属所导致的位错的分裂距离要比通常在弹性各向同性假设下所预期的分裂距离大。这些关于金字塔II结构尺寸和不对称性的发现$〈C+\mathrm{一个}〉$ 位错是理解这些位错在机械应变时如何滑动以及与其他缺陷相互作用或与其他缺陷反应的基础。