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原子尺度断裂模拟进展

RECENT ADVANCES IN ATOMISTIC FRACTURE SIMULATIONS

  • 摘要: 材料/结构的断裂是一个多尺度过程, 绝大多数断裂过程都涉及到原子键的断裂, 因此原子尺度的演化对材料的宏观断裂行为有重要影响. 随着实验技术的飞速进步, 高清电子显微镜已经可以观察到原子尺度的裂纹, 而计算能力的日渐强大使得原子尺度模拟成为揭示实验现象背后的断裂机制、研究众多典型纳米结构材料断裂行为的有力工具. 在本综述文章中, 首先介绍了原子尺度断裂模拟的加载方法, 包括均匀加载、速度梯度加载、K场加载和静水应力加载, 并综合对比了上述加载方法的适用范围, 然后给出了基于原子尺度信息定量计算断裂韧性的方法, 包括能量释放率法、线下面积积分法、临界应力强度因子法、原子尺度内聚力模型法和原子尺度J积分法. 随后介绍了近年来有代表性的不同类型的纳米结构材料(包括单晶、多晶、孪晶等晶体结构, 非晶结构, 异质界面结构)断裂行为模拟研究, 例如钝化处理的单晶硅太阳能电池裂纹抗力大大增加、锂离子电池中锂化浓度控制的硅电极韧脆转变、错配应力驱动界面自发分层一步制备大尺度纳米硅片. 这些研究结果揭示了实验现象背后的机理, 同时和实验结果的一致性也印证了原子尺度模拟的可靠性与准确性. 最后强调了原子尺度模拟面临的一些问题和挑战, 并对将来的发展方向进行了展望.

     

    Abstract: The fracture of materials/structures is a complex and multi-scale process, which is associated with the rupture of atomic bonds. Hence, the evolution of atomistic crack configurations plays a vital role in the macroscopic fracture behavior. With the swift advancement of experimental technology, the cracks at the atomic scale can be detected by high-resolution electron microscopes, and enhanced computing resources have made atomistic simulation a powerful tool to uncover the underlying fracture mechanisms and to investigate the fracture behaviors of various nanostructured materials. In this review article, we first introduced the common loading approaches for atomistic fracture simulations, including uniform loading, velocity gradient loading, K-field loading and hydrostatic stress loading. After comparing these loading approaches, we further summarized a few methods of calculating fracture toughness based on atomic scale information, including energy release rate method, stress-strain curve integral method, critical stress intensity factor method, cohesive zone method at atomic scale and J-integral method at atomic scale. Then, we reviewed the latest computational studies on several typical types of nanostructured materials (including single-crystalline, polycrystalline and twin structures, amorphous structures and heterogeneous interface structures), like the crack resistance of passivated single-crystalline silicon solar cells, the brittle-to-ductile transition of amorphous silicon anodes controlled by lithium concentration in lithium-ion batteries, and the spontaneous interface delamination driven by mismatch stress. These study results revealed the underlying mechanisms behind the experimental phenomena, and were in good agreement with the experimental results. The consistence between simulation and experiment results confirms the reliability and accuracy of atomistic fracture simulations. Finally, we highlighted some challenges faced by atomistic simulations for fracture of materials and proposed the potential future directions.

     

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