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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=762555
• 关键词: Complex; Metastable; Liquids; Phase; Behaviour

Complex Metastable Liquids: Phase Behaviour, Dynamics, and NucleationThe 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.

复杂的亚稳态液体：相行为，动力学和成核液态是我们对物质理解的持续挑战的来源。即使是最简单的经典液体也是一种密集，无序且强烈相互交互的多体系统。因此，液体具有丰富的行为和强大的复杂性，尤其是在分子尺度上。在超冷液体中，液态物理中最重要，最困惑的开放问题的某些问题发生在超冷液体中。玻璃过渡时无定形固体形成的性质是争论的持续来源。同样，还不完全了解了液态的结晶固体的成核。例如对于许多重要系统，我们以定量准确性预测晶体成核速率的能力仍然很差。尽管所有这些问题具有基本的性质，但实际应用比比皆是。例如，金属玻璃合金是一个越来越多的商业感兴趣的领域，例如用于飞机组件。 了解晶体成核对从计算机芯片到药物的广泛生产至关重要。粘性液体的复杂动态特性；以及晶体成核的非平衡动力学。该提案描述了一项研究计划，以研究超冷液体，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。 同时，我们将寻求在上面列出的所有复杂现象变得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的了解。我们将使用分子动力学和蒙特卡洛计算机模拟，从中可以从中获得分子规模的细节和大量特性的估计。例如，将使用伞采样方法评估相图和成核的自由能壁垒，稀有事实的仿真技术（例如正向升压采样）将有助于计算成核速率。 我们选择的研究指示是为了提供广泛的科学兴趣的结果，并创建培训机会，使学生为未来的定量科学工作做好准备。 例如，我们将研究深层冷水中的冰成核，接近在计算机模拟中观察到的液态液相变。 我们还将检查显示出明显的迁移率波动（即动态异质性）的系统中的晶体成核，以探索成核与玻璃形成之间的连接。 我们还将研究异质成核，尤其是在水中，因为这一过程对于理解云形成对气候建模的贡献的重要性。