Fracture is the ultimate source of failure of amorphous carbon (a-C) films; however, it is challenging to measure fracture properties of a-C from nanoindentation tests, and results of reported experiments are not consistent. Here, we use atomic-scale simulations to make quantitative and mechanistic predictions of fracture of a-C. Systematic large-scale K-field controlled atomic-scale simulations of crack propagation are performed for a-C samples with densities of $\rho =2.5$, 3.0, and $3.5{\text{g/cm}}^3$ created by liquid quenches for a range of quench rates ${\dot{T}}_q=10–1000\text{K/ps}$. The simulations show that the crack propagates by nucleation, growth, and coalescence of voids. Distances of $\approx 1\text{nm}$ between nucleated voids result in a brittlelike fracture toughness. We use a crack growth criterion proposed by Drugan, Rice, and Sham [J. Mech. Phys. Solids 30, 447 (1982)] to estimate steady-state fracture toughness based on our short crack-length fracture simulations. Fracture toughness values of $2.4–6.0\text{MPa}\sqrt{\text{m}}$ for initiation and $3–10\text{MPa}\sqrt{\text{m}}$ for the steady-state crack growth are within the experimentally reported range. These findings demonstrate that atomic-scale simulations can provide quantitatively predictive results even for fracture of materials with a ductile crack propagation mechanism.

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通过原子尺度模拟定量预测非晶碳的断裂韧性

断裂是非晶碳（aC）薄膜失效的最终原因。然而，通过纳米压痕测试来测量aC的断裂性能具有挑战性，并且报道的实验结果不一致。在这里，我们使用原子尺度的模拟对aC的断裂进行定量和力学预测。对密度为的aC样品进行了系统的大规模K场控制的裂纹扩展原子级模拟$\rho =2.5$，3.0和 $3.5{\text{克/厘米}}^3$ 在一定范围的淬火速率下由液体淬火产生 ${\dot{Ť}}_q=10–1000\text{千位/秒}$。仿真表明，裂纹通过空洞的形核，生长和聚结而扩展。距离$\approx \mathrm{1个}\text{纳米}$有核空隙之间的断裂导致脆性断裂韧性。我们使用了由Drugan，Rice和Sham [ J. Mech。物理 固体 30，447（1982）〕根据我们的短裂纹长度裂缝模拟来估计稳态断裂韧性。断裂韧性值$2.4–6.0\text{兆帕}\sqrt{\text{米}}$ 用于启动和 $3–10\text{兆帕}\sqrt{\text{米}}$稳态裂纹扩展的数值在实验报告的范围内。这些发现表明，即使对于具有延性裂纹扩展机制的材料断裂，原子尺度的模拟也可以提供定量的预测结果。