Liang Shuai, Hall Kyle Wm, Laaksonen Aatto, Zhang Zhengcai, Kusalik Peter G
1 Key Laboratory of Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangdong Key Laboratory of New and Renewable Energy Research and Development , Guangzhou , People's Republic of China.
2 Department of Chemistry, Temple University , Philadelphia, PA , USA.
Philos Trans A Math Phys Eng Sci. 2019 Jun 3;377(2146):20180167. doi: 10.1098/rsta.2018.0167.
Crystallization in liquids is critical to a range of important processes occurring in physics, chemistry and life sciences. In this article, we review our efforts towards understanding the crystallization mechanisms, where we focus on theoretical modelling and molecular simulations applied to ice and gas hydrate systems. We discuss the order parameters used to characterize molecular ordering processes and how different order parameters offer different perspectives of the underlying mechanisms of crystallization. With extensive simulations of water and gas hydrate systems, we have revealed unexpected defective structures and demonstrated their important roles in crystallization processes. Nucleation of gas hydrates can in most cases be characterized to take place in a two-step mechanism where the nucleation occurs via intermediate metastable precursors, which gradually reorganizes to a stable crystalline phase. We have examined the potential energy landscapes explored by systems during nucleation, and have shown that these landscapes are rugged and funnel-shaped. These insights provide a new framework for understanding nucleation phenomena that has not been addressed in classical nucleation theory. This article is part of the theme issue 'The physics and chemistry of ice: scaffolding across scales, from the viability of life to the formation of planets'.
液体中的结晶对于物理、化学和生命科学中发生的一系列重要过程至关重要。在本文中，我们回顾了我们在理解结晶机制方面所做的努力，我们专注于应用于冰和气体水合物系统的理论建模和分子模拟。我们讨论了用于表征分子有序化过程的序参量，以及不同的序参量如何为结晶的潜在机制提供不同的视角。通过对水和气体水合物系统的广泛模拟，我们揭示了意想不到的缺陷结构，并证明了它们在结晶过程中的重要作用。气体水合物的成核在大多数情况下可以被表征为通过两步机制发生，其中成核通过中间亚稳前体发生，该前体逐渐重新组织成稳定的结晶相。我们研究了系统在成核过程中探索的势能面，并表明这些势能面是崎岖不平且呈漏斗状的。这些见解为理解成核现象提供了一个新的框架，而这在经典成核理论中并未得到解决。本文是主题为“冰的物理和化学：跨越尺度的支架，从生命的可行性到行星的形成”的一部分。
