θ相氮化钽（θ-TaN）的各向异性拉伸强度与断裂机理：基于机器学习势分子动力学的研究
Anisotropic Tensile Strength and Fracture Mechanism of $θ$-TaN: A Machine-Learning Potential Molecular Dynamics Study
AI总结：
本研究采用机器学习势分子动力学模拟，明确了θ-TaN的各向异性拉伸强度、断裂机理及温度效应，为其热管理应用提供原子尺度力学数据。
AI中文摘要：
θ相氮化钽（θ-TaN）兼具金属导电性与极高的热导率，是器件热管理和互连应用的潜在候选材料，但其拉伸强度与断裂行为尚不明确。本研究采用神经演化势分子动力学模拟，探究θ-TaN的各向异性拉伸响应与断裂机理：尺寸收敛测试表明，长度为20 nm的模型足以实现可靠预测；在10^7至10^9 s^-1的应变速率范围内，力学参数变化小于3.5%。结果显示θ-TaN具有显著的拉伸各向异性：c轴方向（[0001]）强度达80.10 GPa、模量达748.63 GPa，但断裂应变仅15.02%；a轴方向（[2-1-10]）强度为56.87 GPa、模量为570.74 GPa，断裂应变则达17.71%。温度从300 K升至900 K时，力学性能近乎线性下降，900 K下仍保留300 K时强度的73%以上。断裂过程无可见位错活动，由解理面选择机制主导：a轴拉伸下为{10-10}棱柱面，c轴拉伸下为(0001)基面。原子位移分析显示，宏观裂纹扩展前会出现局部分离与微孔洞形成，表明该断裂过程为局部键合网络不稳定性驱动的脆性断裂。本研究为评估θ-TaN在热管理应用中的可靠性提供了原子尺度力学数据。
英文摘要：
theta-phase tantalum nitride (theta-TaN) combines metallic conductivity with exceptionally high thermal conductivity, making it a potential material for device thermal management and interconnect applications. However, its tensile strength and fracture behavior remain unclear. Here, we investigate the anisotropic tensile response and fracture mechanism of theta-TaN using neuroevolution-potential molecular dynamics simulations. Size-convergence tests show that a 20 nm long model is sufficient for reliable prediction, and the mechanical parameters vary by less than 3.5% over the strain-rate range of 10^7 to 10^9 s^-1. The results reveal strong tensile anisotropy. The c-axis direction ([0001]) shows a higher strength of 80.10 GPa and modulus of 748.63 GPa, but a lower fracture strain of 15.02%. In contrast, the a-axis direction ([2-1-10]) shows a lower strength of 56.87 GPa and modulus of 570.74 GPa, but a higher fracture strain of 17.71%. From 300 to 900 K, the mechanical properties decrease nearly linearly, while more than 73% of the 300 K strength is retained at 900 K. Fracture occurs without observable dislocation activity and is governed by cleavage-plane selection: {10-10} prismatic planes under a-axis tension and the (0001) basal plane under c-axis tension. Atomic displacement analysis shows that local separation and microvoid formation precede macroscopic crack growth, indicating a brittle fracture process driven by local bond-network instability. These results provide atomic-scale mechanical data for assessing the reliability of theta-TaN in thermal management applications.
