Abstract Point defects play a central role in materials properties. Yet, details regarding their diffusion and aggregation are still largely lacking beyond the monomer and dimer. Using the kinetic Activation Relaxation Technique (k-ART), a recently proposed off-lattice kinetic Monte Carlo method, the energy landscape, kinetics and diffusion mechanisms of point defect in fcc nickel are characterized, providing an exhaustive picture of the motion of one to five vacancies and self-interstitials in this system. Starting with a comparison of the prediction of four empirical potentials — the embedded atom method (EAM), the original modified embedded atom method (MEAM1NN), the second nearest neighbor modified embedded atom method (MEAM2NN) and the Reactive Force Field (ReaxFF) —, it is shown that while both EAM and ReaxFF capture the right physics, EAM provides the overall best agreement with ab initio and molecular dynamics simulations and available experiments both for vacancies and interstitial defect energetics and kinetics. Extensive k-ART simulations using this potential provide complete details of the energy landscape associated with these defects, demonstrated a complex set of mechanisms available to both vacancies and self-interstitials even in a simple environment such as crystalline Ni. We find, in particular, that the diffusion barriers of both vacancies and interstitials do not change monotonically with the cluster size and that some clusters of vacancies diffuse more easily than single ones. As self-interstitial clusters grow, moreover, we show that the fast diffusion takes place from excited states but ground states can act as pinning centers, contrary to what could be expected.

中文翻译：

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镍中点缺陷扩散的动力学活化-弛豫技术研究

摘要 点缺陷在材料性能中起着核心作用。然而，除了单体和二聚体之外，仍然缺乏关于它们扩散和聚集的细节。使用动力学激活松弛技术 (k-ART)，一种最近提出的非晶格动力学蒙特卡罗方法，表征了 fcc 镍中点缺陷的能量景观、动力学和扩散机制，提供了一个到该系统中有五个空缺和自填隙。首先比较四种经验势的预测——嵌入原子法（EAM）、原始修正嵌入原子法（MEAM1NN）、第二近邻修正嵌入原子法（MEAM2NN）和反应力场（ReaxFF）—— ，结果表明，虽然 EAM 和 ReaxFF 都捕捉到了正确的物理，EAM 提供了与从头算和分子动力学模拟以及空位和间隙缺陷能量学和动力学可用实验的总体最佳一致性。使用这种潜力的广泛 k-ART 模拟提供了与这些缺陷相关的能量景观的完整细节，展示了一套复杂的机制，即使在简单的环境（如结晶镍）中也可用于空位和自填隙。我们发现，特别是，空位和间隙的扩散障碍不会随簇大小单调变化，并且一些空位簇比单个空位簇更容易扩散。此外，随着自填隙簇的增长，我们表明快速扩散发生在激发态，但基态可以作为钉扎中心，