Nucleation kinetics in a supercooled metallic glass former
Nucleation kinetics in a supercooled metallic glass former
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DOI：
10.1016/j.actamat.2019.05.057
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发表时间：
2019-08
期刊：
影响因子：
9.4
通讯作者：
F. Puosi;A. Pasturel
中科院分区：
文献类型：
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作者：
F. Puosi;A. Pasturel
我们使用分子动力学模拟来阐明过冷金属玻璃形成器中晶体形核的机制，这种过冷金属玻璃形成器具有基于二十面体对称性的共生晶体和非晶局域有序。在远低于熔点的交叉温度下，我们发现过冷相呈现玻璃化动力学，其中包括斯托克斯-爱因斯坦关系的破裂和空间非均匀动力学的出现。此外，我们还指出，这些现象的产生可能与冷却时二十面体对称性的增加所引起的结构不均匀有关。我们还发现，晶体形核发生在玻璃化转变附近，并且发生在高二十面体对称性的区域，这可以用晶体-液体界面能的强烈降低来解释。这一场景为根据经典成核理论测试成核时间的估计提供了一个框架。更具体地说，我们的发现允许量化过冷相的非均匀特性如何影响这一理论的预测。
We use molecular dynamics simulations to shed light on the mechanism underlying crystal nucleation in a supercooled metallic glass former characterized by a concurring crystal and amorphous local order based on icosahedral symmetry. At a crossover temperature, well below the melting point, we find that the supercooled phase exhibits glassy dynamics which includes a breakdown of the Stokes-Einstein relation and the emergence of spatially heterogeneous dynamics. In addition, we show that the origin of these phenomena can be related to a structural heterogeneity caused by the increase of icosahedral symmetry upon cooling. We also reveal that crystal nucleation occurs close to the glass transition and takes place in regions of high icosahedral symmetry, which can be interpreted by a strong reduction of the crystal-liquid interfacial energy. This scenario provides a framework for testing the estimation of the nucleation time according to the classical nucleation theory. More specifically, our findings allow to quantify how the heterogeneous character of the supercooled phase affects the predictions of this theory.