Signatures of sluggish dynamics and local structural ordering during ice nucleation
Signatures of sluggish dynamics and local structural ordering during ice nucleation
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DOI：
10.1063/5.0083638
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发表时间：
2022-03-21
影响因子：
4.4
通讯作者：
Palmer, Jeremy C.
中科院分区：
文献类型：
--
作者：
Martelli, Fausto;Palmer, Jeremy C.
我们通过无偏经典分子动力学模拟研究了深度过冷条件下水的 ST2 模型中自发结晶的微观路径。在液-液临界点以下淬火后，ST2 模型自发地分别分离成低密度液相 (LDL) 和高密度液相。低密度脂蛋白相的特点是分子流动性较低和结构秩序增强，促进亚临界冰核的形成，经过稳定时间后，该冰核发育成临界核并生长。多晶型选择与亚临界核的发展相一致，并且有利于立方体（Ic）冰而不是六方体（Ih）冰的形成。我们根据冰 Ic 和 Ih 的第二邻壳的对称性差异，根据几何参数合理化多态选择，认为这有利于前者的形成。快速生长的临界核吸收分散在液相中的 Ic 和 Ih 微晶，这是一种具有堆垛层错的晶体。我们的结果与最近对几个系统中非经典成核途径的观察结果一致并扩展了。由 AIP Publishing 独家许可出版。
We investigate the microscopic pathway of spontaneous crystallization in the ST2 model of water under deeply supercooled conditions via unbiased classical molecular dynamics simulations. After quenching below the liquid-liquid critical point, the ST2 model spontaneously separates into low-density liquid (LDL) and high-density liquid phases, respectively. The LDL phase, which is characterized by lower molecular mobility and enhanced structural order, fosters the formation of a sub-critical ice nucleus that, after a stabilization time, develops into the critical nucleus and grows. Polymorphic selection coincides with the development of the sub-critical nucleus and favors the formation of cubic (Ic) over hexagonal (Ih) ice. We rationalize polymorphic selection in terms of geometric arguments based on differences in the symmetry of second neighbor shells of ice Ic and Ih, which are posited to favor formation of the former. The rapidly growing critical nucleus absorbs both Ic and Ih crystallites dispersed in the liquid phase, a crystal with stacking faults. Our results are consistent with, and expand upon, recent observations of non-classical nucleation pathways in several systems. Published under an exclusive license by AIP Publishing.