The transition from Hall-Petch to inverse Hall-Petch behaviors in nanocrystalline semiconductors is complex and remains poorly understood, despite its importance to the mechanical performance of these materials. In this study, we used molecular dynamics simulations with a machine-learning force field (ML-FF MD) to examine the shear deformation and failure mechanisms of nanocrystalline cadmium telluride (n-CdTe) across grain sizes ranging from 4.62 nm to 18.47 nm. Our results reveal a transition from Hall-Petch to inverse Hall-Petch behavior in n-CdTe at a critical grain size of ∼9.79 nm, where the material's maximum shear strength reaches about 1.23 GPa. This transition is driven by varying probabilities of phase transitions from the zinc-blende to the β-Sn-like CdTe phase, due to the competition between shear localization and the availability of nucleation sites. Importantly, regardless of grain sizes, this phase transition often starts near grain boundaries (GBs), causing volume shrinkage and tensile stresses at GBs, further leading to fractures between grains. These findings offer valuable insights into the underlying mechanisms driving the transition from Hall-Petch to inverse Hall-Petch behavior as grain size decreases, as well as the failure behaviors observed in n-CdTe and other semiconductor materials.

中文翻译：

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解开纳米晶 CdTe 中 Hall-Petch 到逆 Hall-Petch 转变的解析


纳米晶半导体中从 Hall-Petch 行为到反向 Hall-Petch 行为的转变很复杂，尽管它对这些材料的机械性能很重要，但人们仍然知之甚少。在这项研究中，我们使用了具有机器学习力场 （ML-FF MD） 的分子动力学模拟来研究纳米晶碲化镉 （n-CdTe） 在 4.62 nm 至 18.47 nm 晶粒尺寸的剪切变形和失效机制。我们的结果揭示了在 ∼9.79 nm 的临界晶粒尺寸下，n-CdTe 中从 Hall-Petch 转变为逆 Hall-Petch 行为，其中材料的最大剪切强度达到约 1.23 GPa。由于剪切定位和成核位点可用性之间的竞争，这种转变是由从闪锌矿到类 β-Sn 的 CdTe 相变的不同概率驱动的。重要的是，无论晶粒尺寸如何，这种相变通常从晶界 （GB） 附近开始，导致 GB 处的体积收缩和拉伸应力，进一步导致晶粒之间的断裂。这些发现为随着晶粒尺寸的减小而驱动从 Hall-Petch 转变为逆 Hall-Petch 行为的潜在机制，以及在 n-CdTe 和其他半导体材料中观察到的失效行为提供了有价值的见解。