Theoretical and Applied Mechanics Program, Northwestern University, Evanston, IL 60208.
Department of Materials Science and NanoEngineering, Rice University, Houston, TX 77005.
Proc Natl Acad Sci U S A. 2022 Nov 8;119(45):e2206756119. doi: 10.1073/pnas.2206756119. Epub 2022 Nov 4.
Quantifying the intrinsic mechanical properties of two-dimensional (2D) materials is essential to predict the long-term reliability of materials and systems in emerging applications ranging from energy to health to next-generation sensors and electronics. Currently, measurements of fracture toughness and identification of associated atomistic mechanisms remain challenging. Herein, we report an integrated experimental-computational framework in which in-situ high-resolution transmission electron microscopy (HRTEM) measurements of the intrinsic fracture energy of monolayer MoS and MoSe are in good agreement with atomistic model predictions based on an accurately parameterized interatomic potential. Changes in crystalline structures at the crack tip and crack edges, as observed in in-situ HRTEM crack extension tests, are properly predicted. Such a good agreement is the result of including large deformation pathways and phase transitions in the parameterization of the inter-atomic potential. The established framework emerges as a robust approach to determine the predictive capabilities of molecular dynamics models employed in the screening of 2D materials, in the spirit of the materials genome initiative. Moreover, it enables device-level predictions with superior accuracy (e.g., fatigue lifetime predictions of electro- and opto-electronic nanodevices).
量化二维（2D）材料的固有力学性能对于预测从能源到健康，再到下一代传感器和电子等新兴应用中材料和系统的长期可靠性至关重要。目前，测量断裂韧性和识别相关的原子机制仍然具有挑战性。在此，我们报告了一个集成的实验-计算框架，其中单层 MoS 和 MoSe 的本征断裂能的原位高分辨率透射电子显微镜（HRTEM）测量结果与基于精确参数化原子间势的原子模型预测结果非常吻合。在原位 HRTEM 裂纹扩展测试中观察到的裂纹尖端和裂纹边缘处的晶体结构变化得到了很好的预测。这种良好的一致性是在原子间势的参数化中包含大变形途径和相变的结果。该框架的建立为在二维材料筛选中使用分子动力学模型的预测能力提供了一种稳健的方法，符合材料基因组计划的精神。此外，它还能够进行具有更高精度的器件级预测（例如，电和光电纳米器件的疲劳寿命预测）。
