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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=683397
• 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.

复合亚稳液体：相行为，动力学和成核 * 液态是我们理解物质的挑战的持久来源。即使是最简单的经典液体，也是一个稠密、无序、强相互作用的多体系统。因此，液体呈现给我们丰富的行为和令人生畏的复杂性，特别是在分子尺度上。在液态物理学中，一些最重要和最令人困惑的未决问题发生在过冷液体中。在玻璃化转变时无定形固体形成的性质是一个持续的争论来源。类似地，从液态结晶固体的成核也不完全理解;例如，我们预测晶体成核速率与定量准确性的能力仍然很差，许多重要的系统。虽然所有这些问题都是基本性质的，但实际应用却比比皆是。例如，金属玻璃合金是商业兴趣的增长领域，例如用于飞机部件。 理解晶体成核在从计算机芯片到制药的广泛制造业中至关重要。在过冷液体的背景下，一些独特的和复杂的现象收敛：亚稳相的热力学;粘性液体的复杂动力学性质;和晶体成核的非平衡动力学。该提案描述了一个研究过冷液体的研究计划，重点是水中的成核现象，因为它的复杂性及其在自然科学和工程中的普遍重要性。 与此同时，我们将寻求在上述所有复杂现象相互交织的条件下研究物质，以寻求对亚稳态系统的更广泛理解。我们将使用分子动力学和蒙特卡罗计算机模拟，从分子尺度的细节和估计散装性能可能会得到。例如，相图和成核的自由能垒将使用伞形取样方法进行评估，而稀有事件模拟技术，如前向通量取样，将有助于计算成核率。 我们的研究方向选择提供广泛的科学兴趣的结果，并创造培训机会，为学生在定量科学的未来工作做好准备。 例如，我们将研究深过冷水中的冰成核，接近于在计算机模拟中观察到的拟议的液-液相变。 我们还将研究系统中的晶体成核表现出明显的迁移率波动（即动态异质性），探索成核和玻璃形成之间的联系。 我们还将研究异质成核，特别是在水中，由于这个过程的重要性，了解云的形成气候模拟的贡献。