Point-defect avalanches mediate grain boundary diffusion
Point-defect avalanches mediate grain boundary diffusion
复制标题
DOI：
10.1038/s43246-022-00314-7
复制
发表时间：
2022-06
影响因子：
7.8
通讯作者：
I. Chesser;Y. Mishin
中科院分区：
文献类型：
--
作者：
I. Chesser;Y. Mishin
多晶材料中的晶界扩散是一种具有重大基础意义和实际意义的物理现象。尽管沿晶界的加速原子传输已为人所知数十年，但对扩散机制的原子级理解仍然很差。以前的原子模拟主要关注晶界结构有序的低温或高度无序的高温。在这里，我们在与应用最相关的中间温度下进行晶界扩散的分子动力学模拟。这项工作的一个令人惊讶的结果是观察到间歇性 GB 扩散行为及其强烈的系统尺寸依赖性，这在以前的工作中是未曾见过的。研究发现这两种效应均源于热激活点缺陷雪崩。我们确定了雪崩的长度和时间尺度，并将其形成与部分无序系统中的动态异质性联系起来。我们的研究结果对纳米级材料中晶界扩散和质量传输的未来计算机建模具有影响。
Grain boundary diffusion in polycrystalline materials is a physical phenomenon of great fundamental interest and practical significance. Although accelerated atomic transport along grain boundaries has been known for decades, atomic-level understanding of diffusion mechanisms remains poor. Previous atomistic simulations focused on low temperatures where the grain boundary structure is ordered or high temperatures where it is highly disordered. Here, we conduct molecular dynamics simulations of grain boundary diffusion at intermediate temperatures most relevant to applications. A surprising result of this work is the observation of intermittent GB diffusion behavior and its strong system-size dependence unseen in previous work. Both effects are found to originate from thermally activated point-defect avalanches. We identify the length and time scales of the avalanches and link their formation to dynamic heterogeneity in partially disordered systems. Our findings have implications for future computer modeling of grain boundary diffusion and mass transport in nano-scale materials.