Nucleation and glassy dynamics in liquids and nanoparticles

水是地球上的一种液体，是生命所必需的，是一种奇怪的物质。例如，与简单物质相比，其热膨胀系数、比热和可压缩性均表现出异常行为，后两者在低温下出现发散。一种解释水异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，它们被一条一阶跃迁线分开，这条跃迁线终止于液-液临界点（LLCP），这种临界点被认为存在于压力在50-200MPa之间，温度低于-50°C。尽管越来越多的实验证据与这一假设相一致，而且越来越多的计算机模拟的类水模型也展示了这种奇特的现象，但没有一个实验直接显示了液-液转变，因为没有一个实验成功地避免了快速结晶，这阻碍了在所提出的LLCP的温度和压力范围内研究液态。****** LLCP假说是液态物理丰富的象征。另外两种对材料科学具有根本重要性的液态现象是玻璃化转变，即液体的粘度急剧增加，直到它变成无定形固体，以及晶体成核，即液体向有序的结晶固体转变的过程。我的研究的首要目标是使用计算机模拟，以更好地了解LLCP，玻璃动力学，晶体成核，以及它们之间的连接。******一个被提出的想法是研究纳米水滴，其表面张力和小半径可以在LLCP提出的范围内产生高内压。它们是微型压力室。在纳米液滴中，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遥不可及的条件下研究液态水。为了统一我们对水、二氧化硅和相关网络形成液体的理解，我们希望继续在将它们的性质映射到四价胶体体系方面取得进展，四价胶体体系具有相对简单、可调的相互作用，更容易理解。我们希望进一步发展我们的惊人发现，即一种模型材料，它具有冷却时熔化的潜在有用特性，与人们通常期望的完全相反，并找到在真实胶体系统中复制这种行为的方法。最后，在成功应用统计力学和模拟技术研究液体的基础上，我们建议研究磁性纳米颗粒，以及如何将它们用于组织修复。

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 -50°C. 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.