Atomistic insight into the non-classical nucleation mechanism during solidification in Ni.
Atomistic insight into the non-classical nucleation mechanism during solidification in Ni.
复制标题
DOI：
10.1063/1.4980082
复制
发表时间：
2017-04
期刊：
影响因子：
--
通讯作者：
Grisell Díaz Leines;R. Drautz;J. Rogal
中科院分区：
文献类型：
--
作者：
Grisell Díaz Leines;R. Drautz;J. Rogal
成核是结晶过程中的关键步骤，但对基本原子过程的完整理解仍然是难以捉摸的。我们研究的形核机制，在镍凝固过程中的各种过冷度使用过渡路径抽样模拟。我们得到的自由能垒和速率常数的温度依赖性与经典成核理论和实验的预测是一致的。然而，我们的过渡路径系综的分析揭示了一种机制，偏离经典的成核图片：生长的固体团簇主要是非球形的形状，由面心立方和随机六角形紧密堆积的配位原子包围的云的预结构液体。成核起始于过冷液体的区域，其特征在于具有预定多晶型物选择的结构特征的高取向顺序。这些结果提供原子的洞察力，不仅成核机制的镍，但也到的作用，作为结晶的前体的预定的液体区域。
Nucleation is a key step during crystallization, but a complete understanding of the fundamental atomistic processes remains elusive. We investigate the mechanism of nucleation during solidification in nickel for various undercoolings using transition path sampling simulations. The temperature dependence of the free energy barriers and rate constants that we obtain is consistent with the predictions of classical nucleation theory and experiments. However, our analysis of the transition path ensemble reveals a mechanism that deviates from the classical picture of nucleation: the growing solid clusters have predominantly non-spherical shapes and consist of face-centered-cubic and random hexagonal-close-packed coordinated atoms surrounded by a cloud of prestructured liquid. The nucleation initiates in regions of supercooled liquid that are characterized by a high orientational order with structural features that predetermine the polymorph selection. These results provide atomistic insight not only into the nucleation mechanism of nickel but also into the role of the preordered liquid regions as precursors for crystallization.