In bulk crystals, the kinetics of dislocations is usually hindered by the twining boundaries (TB) or grain boundaries (GB), rendering the well‐known grain boundary strengthening effects. Nevertheless, here it is found that in 2D rhenium disulfide (ReS₂), twinning is much easier than dislocation slip. Consequently, the highly mobile TBs or GBs are inversely pinned by the relatively immobile dislocations. Due to the strong in‐plane covalent bonding, the GBs in high‐symmetry 2D materials such as graphene which consists of defects are immobile at room temperature. In contrast, in monoclinic 2D ReS₂ several types of GBs (including TBs) can be readily generated and driven by mechanical loading. A complete library of the GBs in 2D ReS₂ is established by the (in situ) atomic‐scale transmission electron microscopy (TEM) characterizations and density functional theory (DFT) calculations. The twinning (shear) stresses for 2D ReS₂ are estimated as low as 4–30 MPa, one or two orders of magnitude lower than the traditional bulk materials. Full elucidation on the GB structures and especially the intriguing GB kinetics in such anisotropic 2D materials are of fundamental importance to understand the structure–property relationships and develop strain‐tunable applications for 2D materials in future.

中文翻译：

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二维单斜R二硫化物中的可移动和固定晶粒边界

在块状晶体中，位错的动力学通常受孪晶界（TB）或晶界（GB）的阻碍，从而产生了众所周知的晶界强化效应。尽管如此，这里发现在2D二硫化rh（ReS ₂）中，孪晶比位错滑移容易得多。因此，高移动性的TB或GB被相对固定的位错反向固定。由于强大的面内共价键，由缺陷组成的高对称2D材料（如石墨烯）中的GB在室温下无法移动。相反，在单斜2D ReS _2中，可以通过机械负载轻松生成和驱动几种类型的GB（包括TB）。2D ReS _2中GB的完整库通过（原位）原子尺度透射电子显微镜（TEM）表征和密度泛函理论（DFT）计算来建立。二维ReS ₂的孪生（剪切）应力估计低至4–30 MPa，比传统的散装材料低一两个数量级。充分了解此类各向异性2D材料中的GB结构，尤其是有趣的GB动力学，对于理解结构与性质之间的关系以及在将来开发2D材料的可应变应用至关重要。