Abstract As is known to all, diamond is the hardest natural substance. The synthesis of harder materials than the natural diamond is very favorable but challenging. It has been found that the introduction of nanotwinned (NT) structure into diamond could be an effective approach to improve the hardness of diamond. Nevertheless, the fundamental understanding of the strengthening characteristics by NT structure is still ambiguous. In this work, we unveil the effect of NT structure on the deformation mechanism and mechanical properties of diamond at the atomic scale by virtue of atomistic simulations. Interestingly, the hardness measured by nanoindentation shows a positive correlation to the twin spacing instead of the inverse Hall-Petch effect extensively discovered in many traditional metal materials. However, it is not the smallest twin spacing achieving the highest tensile strength, indicating the existence of twin-spacing-induced inverse Hall-Petch effect in NT diamond during tensile deformation. The specific deformation mechanisms are investigated which are capable of providing an explicit explanation for the observed mechanical characteristics.

中文翻译：

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通过原子模拟了解纳米孪晶金刚石的机械特性

摘要 众所周知，金刚石是最坚硬的天然物质。比天然金刚石更硬的材料的合成非常有利但具有挑战性。已经发现，在金刚石中引入纳米孪晶（NT）结构可能是提高金刚石硬度的有效途径。尽管如此，对NT结构的强化特性的基本理解仍然模糊不清。在这项工作中，我们通过原子模拟在原子尺度上揭示了 NT 结构对金刚石变形机制和机械性能的影响。有趣的是，纳米压痕测量的硬度与孪晶间距呈正相关，而不是在许多传统金属材料中广泛发现的反向霍尔-佩奇效应。然而，它不是达到最高拉伸强度的最小孪晶间距，表明 NT 金刚石在拉伸变形过程中存在孪晶间距诱导的逆霍尔-佩奇效应。研究了能够为观察到的机械特性提供明确解释的特定变形机制。