Grain growth in polycrystalline materials can be impeded by grain boundary (GB) stagnation. Using atomistic simulations, we observed that during GB migration, the disruptive jumps of a few GB atoms can disturb the original ordered collective movement of GB atoms, leading to the stagnation of the entire GB. These disruptive atomic jumps can be activated by both high driving forces and high temperatures, with even jumps of a few atoms capable of causing the stagnation of an entire GB. This mechanism also explains the non-Arrhenius behavior observed in some GBs. Additionally, a large model size could increase the rate of disruptive atomic jumps, and a clear transition in thermal behavior is observed with the increase of the GB size in GBs exhibiting clear thermally activated stagnation. Our further investigation shows that the disruptive atoms involved in these jumps do not differ from other GB atoms in terms of atomic energy, volume, density, local entropy, or Voronoi tessellation, and no “jam transition” was observed in the energy barrier spectra. This fact makes those disruptive jumps challenging to detect. To address this issue, we propose a displacement vector analysis method that effectively identifies these subtle disruptive jumps.

中文翻译：

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破坏性原子跳跃导致晶界停滞


多晶材料中的晶粒生长可能会因晶界 (GB) 停滞而受到阻碍。通过原子模拟，我们观察到在GB迁移过程中，少数GB原子的破坏性跳跃会扰乱GB原子原来有序的集体运动，导致整个GB的停滞。这些破坏性的原子跳跃可以由高驱动力和高温激活，甚至几个原子的跳跃也能导致整个GB的停滞。这种机制也解释了在一些 GB 中观察到的非阿累尼乌斯行为。此外，大的模型尺寸可能会增加破坏性原子跳跃的速率，并且随着晶界尺寸的增加，观察到热行为的明显转变，表现出明显的热激活停滞。我们的进一步研究表明，参与这些跳跃的破坏性原子在原子能、体积、密度、局部熵或沃罗诺伊镶嵌方面与其他GB原子没有区别，并且在能垒光谱中没有观察到“堵塞跃迁”。这一事实使得这些破坏性跳跃难以检测。为了解决这个问题，我们提出了一种位移矢量分析方法，可以有效地识别这些微妙的破坏性跳跃。