镍中辐射诱导碰撞级联中的电子效应
Electronic effects in radiation-induced collision cascades in nickel
AI总结：
本研究探讨了一种无参数双温分子动力学模型在镍中辐射诱导碰撞级联模拟中的应用，该模型通过电子密度依赖耦合准确捕捉各阶段能量损失，与实验结果一致，显著提升了辐射损伤预测的可靠性。
摘要：
在数百万原子规模的辐射诱导碰撞级联模拟中，准确处理电子效应对于可靠预测初级辐射损伤至关重要。在本研究中，我们探讨了最近开发的一种双温分子动力学模型的性能，该模型实现了电子与原子子系统的电子密度依赖耦合，用于镍中的级联模拟。我们表明，该无参数模型真实地捕捉了高度非平衡级联过程所有阶段的瞬时能量损失。模拟预测了两种不同的耦合机制，分别对应于级联早期阶段的快速电子阻止能量损失和后期阶段的电子-声子耦合机制，而无需使用单独的耦合项。级联动力学的中间阶段显示出子系统之间复杂的能量转移，这无法通过与电子阻止或电子-声子耦合理论的比较来验证。因此，我们将预测的原子混合（对中间级联阶段的能量损失敏感）与实验离子束混合测量进行了比较。我们发现与实验结果良好吻合，验证了中间级联阶段的耦合模型。最终缺陷数量和团簇尺寸的预测与基于常规电子阻止方法的预测一致，同时显著减少了由于不同耦合项阈值的任意选择而导致的常规模型预测的理论不确定性。我们的结果在镍级联损伤预测中代表了显著改进，为辐射损伤模拟中的电子密度依赖耦合模型提供了总体验证。
英文摘要：
The accurate treatment of electronic effects in multi-million atom simulations of radiation-induced collision cascades is crucial for reliable predictions of primary radiation damage. In this work, we explore the performance of a recently developed two-temperature molecular dynamics model implementing an electron density-dependent coupling of electronic and atomic subsystems for cascade simulations in nickel. We show that the parameter-free model realistically captures the instantaneous energy losses during all stages of the highly non-equilibrium cascade process. Simulations predict two distinct coupling regimes, corresponding to the rapid electronic stopping energy losses in the early stages of the cascade and to the electron-phonon coupling mechanism in the later stages, without the use of separate coupling terms. The intermediate stage of the cascade dynamics displays a complex energy transfer between the subsystems, which cannot be validated by comparison to either electronic stopping or electron-phonon coupling theories. We therefore compare the predicted atomic mixing, which is sensitive to the energy losses during the intermediate cascade stage, with experimental ion beam mixing measurements. We find good agreement with the experiments, validating the coupling model for the intermediate stage of cascades. Predictions of final defect numbers and cluster sizes are found in line with the predictions of conventional electronic stopping-based methods, while significantly reducing the theoretical uncertainty in the predictions of conventional models stemming from arbitrary choices of thresholds for different coupling terms. Our results represent a notable improvement in cascade damage predictions in nickel, providing validation of the electron density-dependent coupling model for radiation damage simulations in general.
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