非均匀籽晶分子动力学研究晶体表面的冰成核能力
Heterogeneous Seeded Molecular Dynamics as a Tool to Probe the Ice Nucleating Ability of Crystalline Surfaces
摘要：
冰成核在许多自然和技术过程中起着重要的作用，但由于所涉及的时间短（ns）和长度尺度短（nm），因此实验研究具有挑战性。另一方面，传统的分子模拟很难处理临界冰核形成所需的相对较长的时间尺度。解决这个问题的一种方法是利用自由能或路径采样技术。不幸的是，这些计算成本很高。种子分子动力学是一种要求低得多的替代方法，已经成功地应用于研究水的均匀冻结。然而，在非均质冰成核的情况下，自然界最喜欢的形成冰的途径，必须在冰种子和感兴趣的基质之间建立一系列合适的界面-这不是一项简单的任务。在本文中，我们提出了一个异质SEEDing方法（HSEED），利用随机结构搜索框架来解决冰基板的挑战，从而使种子分子动力学模拟的异质冰成核晶体表面。我们验证HSEED框架通过研究成核的冰：（i）模型晶体表面，使用粗粒度mW模型;和（ii）胆固醇晶体，采用完全原子的TIP 4P/冰水模型。我们表明，HSEED技术产生的结果与metadaptics和前向通量采样模拟非常一致。由于其计算效率，HSEED方法允许人们快速评估整个晶体基质库的冰成核能力-这是大气科学等领域期待已久的计算发展。
英文摘要：
Ice nucleation plays a significant role in a large number of natural and technological processes, but it is challenging to investigate experimentally because of the small time (ns) and short length scales (nm) involved. On the other hand, conventional molecular simulations struggle to cope with the relatively long timescale required for critical ice nuclei to form. One way to tackle this issue is to take advantage of free energy or path sampling techniques. Unfortunately, these are computationally costly. Seeded molecular dynamics is a much less demanding alternative that has been successfully applied already to study the homogeneous freezing of water. However, in the case of heterogeneous ice nucleation, nature's favourite route to form ice, an array of suitable interfaces between the ice seeds and the substrate of interest has to be built - and this is no trivial task. In this paper, we present a Heterogeneous SEEDing approach (HSEED) which harnesses a random structure search framework to tackle the ice-substrate challenge, thus enabling seeded molecular dynamics simulations of heterogeneous ice nucleation on crystalline surfaces. We validate the HSEED framework by investigating the nucleation of ice on: (i) model crystalline surfaces, using the coarse-grained mW model; and (ii) cholesterol crystals, employing the fully atomistic TIP4P/Ice water model. We show that the HSEED technique yields results in excellent agreement with both metadynamics and forward flux sampling simulations. Because of its computational efficiency, the HSEED method allows one to rapidly assess the ice nucleation ability of whole libraries of crystalline substrates - a long-awaited computational development in e.g. atmospheric science.
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