Nucleation and glassy dynamics in liquids and nanoparticles

液体和纳米颗粒中的成核和玻璃态动力学

• 批准号: RGPIN-2017-05569
• 负责人: SaikaVoivod, Ivan
• 金额: $ 1.53万
• 依托单位: Memorial University of Newfoundland
• 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=711260
• 关键词: Nucleation; glassy; dynamics; liquids; nanoparticles

Water, the liquid that bathes our planet and is essential for life, is a strange substance. For example, its thermal expansion coefficient, specific heat and compressibility all show anomalous behavior compared to simple substances, the latter two appearing to diverge at low temperature. A hypothesis that accounts for water's anomalous behaviour sounds stranger still: the existence of two distinct metastable liquid forms of water separated by a line of first order transitions that terminates in a liquid-liquid critical point (LLCP) thought to exist at pressures between 50-200MPa and temperatures below -50C. Despite an increasing body of experimental evidence consistent with this hypothesis and a growing number of computer simulations of water-like models that exhibit this exotic phenomenon, no experiment has directly shown the liquid-liquid transition, since none has successfully avoided the rapid crystallization that prevents the study of the liquid state in the temperature and pressure range of the proposed LLCP. The LLCP hypothesis is emblematic of the richness of liquid state physics. Two other liquid state phenomena of fundamental importance to materials science are the glass transition, the dramatic increase in viscosity of a liquid until it becomes an amorphous solid, and crystal nucleation, the process that initiates the transformation of a liquid to an ordered, crystalline solid. The overarching goal of my research is to use computer simulations to better understand the LLCP, glassy dynamics, crystal nucleation, and the connections between them. One proposed idea is to study water nanodroplets, the surface tension and small radii of which can produce high internal pressures in the range proposed for the LLCP. They are miniature pressure chambers. Nucleation is also suppressed in nanodroplets, so they may prove to be ideal experimental probes to study liquid water at conditions that so far have remained out of reach. In terms of unifying our understanding of water, silica, and related network-forming liquids, we want to continue our progress in mapping their properties onto tetravalent colloidal systems, which have relatively simple, tunable interactions that are easier to understand. We want to further develop our surprising discovery of a model material with the potentially useful property of melting on cooling, the exact opposite of what one typically expects, and find ways of replicating the behaviour in real colloidal systems. Finally, building on success in applying the statistical mechanical and simulation techniques developed for the study of liquids to interdisciplinary work on fish-derived antimicrobial peptides, a lung surfactant protein and an anti-cell-proliferative drug candidate, we propose to study magnetic nanoparticles and how they can be used in tissue repair.

水是沐浴我们星球的液体，对生命至关重要，是一种奇怪的物质。例如，与简单物质相比，其热膨胀系数，特异性热和可压缩性均显示出异常的行为，后两个在低温下似乎有所不同。一个说明水异常行为的假设听起来仍然很陌生：存在两种不同的亚稳态液体形式的水，这些液体形式的水被一阶跃迁线分离，这些过渡终止在液态液体临界点（LLCP）中终止在50-200MPA和低于-50c的温度之间存在的压力。尽管越来越多的实验证据与该假设以及表现出这种外来现象的水样模型的越来越多的计算机模拟一致，但没有任何实验直接显示液态液体过渡，因为没有一个成功地避免了避免了液态液态的快速结晶，从而阻止了液态液态在提议的LLCP的温度和压力范围内的研究。 LLCP假设是液态物理学丰富性的象征。材料科学基本重要性的另外两个液态现象是玻璃转变，液体粘度的急剧增加，直到它变成无定形的固体和晶体成核，这是启动液体向有序的结晶固体转化的过程。我的研究的总体目标是使用计算机模拟更好地了解LLCP，玻璃动力学，晶体成核及其之间的连接。 一个建议的想法是研究水纳米圆形，表面张力和小半径可以在建议的LLCP范围内产生高内部压力。 它们是微型压力室。成核也抑制了纳米光中的成核，因此它们可能被证明是在迄今为止尚无法到达的条件下研究液态水的理想实验探针。 在统一我们对水，二氧化硅和相关网络形成的液体的理解方面，我们希望继续将其特性映射到四位价值胶体系统中，这些胶体系统具有相对简单，可调的相互作用，易于理解。 我们希望进一步开发出令人惊讶的模型材料，并具有在冷却方面融化的潜在有用的属性，这与人们通常期望的完全相反，并找到在实际胶体系统中复制行为的方法。 最后，基于成功应用用于研究液体研究的统计机械和仿真技术，用于研究鱼类衍生的抗微生物肽，肺表面活性剂蛋白和抗细胞促销药物候选药物的跨学科工作，我们建议研究磁性纳米颗粒以及如何用于组织修复。