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.

水是一种奇怪的物质，它沐浴着我们的星球，是生命所必需的。例如，它的热膨胀系数，比热和压缩性都显示出与简单物质相比的异常行为，后两者在低温下出现发散。一个解释水的反常行为的假设听起来更奇怪：存在两种不同的亚稳态液体形式的水，它们被一阶跃迁线分开，终止于液-液临界点（LLCP），该临界点被认为存在于50- 200 MPa之间的压力和-50 ℃以下的温度。尽管越来越多的实验证据与这一假设一致，并且越来越多的计算机模拟显示出这种奇异现象的水状模型，但没有实验直接显示出液-液转变，因为没有一个实验成功地避免了快速结晶，这阻止了在所提出的LLCP的温度和压力范围内研究液态。 LLCP假说是液态物理丰富性的象征。对材料科学具有根本重要性的另外两种液态现象是玻璃化转变，即液体粘度急剧增加直到其变成无定形固体，以及晶体成核，即引发液体向有序结晶固体转变的过程。我研究的首要目标是使用计算机模拟来更好地理解LLCP，玻璃态动力学，晶体成核以及它们之间的联系。 一个提议的想法是研究水纳米滴，其表面张力和小半径可以在LLCP的建议范围内产生高的内部压力。 它们是微型压力舱。纳米液滴中的成核也受到抑制，因此它们可能被证明是理想的实验探针，可以在迄今为止仍然无法达到的条件下研究液态水。 在统一我们对水，二氧化硅和相关网络形成液体的理解方面，我们希望继续将它们的性质映射到四价胶体系统上，这些系统具有相对简单，可调的相互作用，更容易理解。 我们希望进一步发展我们令人惊讶的发现，即具有冷却时熔化的潜在有用性质的模型材料，与人们通常预期的完全相反，并找到在真实的胶体系统中复制这种行为的方法。 最后，建立在成功应用统计力学和模拟技术开发的研究液体跨学科工作的鱼源性抗菌肽，肺表面活性蛋白和抗细胞增殖药物候选人，我们建议研究磁性纳米粒子，以及它们如何可以用于组织修复。