Complex Metastable Liquids: Phase Behaviour, Dynamics, and Nucleation

复杂亚稳态液体：相行为、动力学和成核

• 批准号: RGPIN-2017-04512
• 负责人: Poole, Peter
• 金额: $ 2.19万
• 依托单位: St. Francis Xavier University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=710041
• 关键词: Complex; Metastable; Liquids; Phase; Behaviour

Complex Metastable Liquids: Phase Behaviour, Dynamics, and Nucleation The liquid state is an enduring source of challenges for our understanding of matter. Even the simplest classical liquid is a dense, disordered, and strongly-interacting many-body system. Liquids thus present us with rich behavior and formidable complexity, especially at the molecular scale. Some of the most important and perplexing open questions in liquid-state physics occur in supercooled liquids. The nature of amorphous solid formation at the glass transition is a continuing source of debate. Similarly, the nucleation of crystalline solids from the liquid state is also incompletely understood; e.g. our ability to predict crystal nucleation rates with quantitative accuracy remains poor for many important systems. While all these questions are of a fundamental nature, practical applications abound. For example, metallic glass alloys are a growing area of commercial interest, e.g. for aircraft components. Understanding crystal nucleation is vital in a wide swathe of manufacturing, from computer chips to pharmaceuticals. In the context of supercooled liquids, a number of distinct and complex phenomena converge: the thermodynamics of metastable phases; the complex dynamic properties of viscous liquids; and the non-equilibrium kinetics of crystal nucleation. This proposal describes a program of research to investigate supercooled liquids, with a focus on nucleation phenomena in water, because of its complexity, and its pervasive importance across the natural sciences and engineering. At the same time, we will seek to study substances under conditions in which all the complex phenomena listed above become intertwined, in order to seek a broader understanding of metastable systems. We will use molecular dynamics and Monte Carlo computer simulations, from which both molecular-scale details and estimates of bulk properties may be obtained. For example, phase diagrams and free energy barriers for nucleation will be evaluated using umbrella sampling methods, and rare-event simulation techniques such as forward-flux sampling will facilitate calculation of nucleation rates. Our research directions are chosen to provide results of wide scientific interest, and to create training opportunities that prepare students for future work in the quantitative sciences. For example, we will study ice nucleation in deeply supercooled water, close to the proposed liquid-liquid phase transition that has been observed in computer simulations. We will also examine crystal nucleation in systems exhibiting pronounced mobility fluctuations (i.e. dynamical heterogeneities) to explore connections between nucleation and glass formation. We will also study heterogeneous nucleation, especially in water, due to the importance of this process for understanding the contributions of cloud formation to climate modeling.

复杂的亚稳液体：相行为、动力学和成核 液态是我们理解物质的一个持久的挑战来源。即使是最简单的经典液体，也是一个稠密、无序、相互作用强烈的多体系统。因此，液体向我们展示了丰富的行为和令人敬畏的复杂性，特别是在分子尺度上。 液态物理学中一些最重要和最令人困惑的悬而未决的问题发生在过冷液体中。玻璃化转变时无定形固体形成的性质是一个持续争论的来源。同样，结晶固体从液态成核也不完全了解；例如，对于许多重要的系统，我们预测晶体成核速率的能力仍然很差。虽然所有这些问题都是根本性的，但实际应用却比比皆是。例如，金属玻璃合金是一个日益受到商业关注的领域，例如用于飞机部件。从计算机芯片到制药，了解晶体成核在广泛的制造业中至关重要。 在过冷液体的背景下，许多独特而复杂的现象汇聚在一起：亚稳态相的热力学；粘性液体的复杂动力学性质；以及结晶成核的非平衡动力学。这项建议描述了一项研究过冷液体的计划，重点是水中的成核现象，因为它的复杂性，以及它在自然科学和工程中的普遍重要性。同时，我们将寻求在上述所有复杂现象交织在一起的条件下研究物质，以寻求对亚稳态系统的更广泛的理解。 我们将使用分子动力学和蒙特卡罗计算机模拟，从中可以获得分子尺度的细节和整体性质的估计。例如，将使用伞形抽样方法评估相图和成核的自由能垒，而像正向通量抽样这样的罕见事件模拟技术将有助于计算成核速率。我们选择研究方向是为了提供引起广泛科学兴趣的结果，并创造培训机会，为学生未来在量化科学方面的工作做好准备。例如，我们将研究深度过冷水中的冰成核，这接近于在计算机模拟中观察到的液-液相变。我们还将研究具有明显迁移率波动(即动力学异质性)的系统中的晶体成核，以探索成核和玻璃形成之间的联系。我们还将研究非均相成核，特别是在水中，因为这一过程对于理解云形成对气候模拟的贡献非常重要。