Glass Transitions, Polyamorphic Transitions, and Chemical Order Freezing Transitions, in Liquids and Other Complex Systems

该项目旨在研究通过“超淬火”在极短时间内形成的玻璃。几十年来，超淬火技术一直被用于玻璃化“不良”玻璃形成物，但从未被系统地应用于探索普通玻璃形成物的高温结构和性能。在没有振动激励的情况下检查玻璃成型液体特征的可能性是本研究的中心目标。在之前的资助期间获得了一些关键的结果，支持拓扑缺陷作为玻璃中的初等激发的概念，并且将进行适当发展这一想法所需的实验。将对含有氰化物离子CN-等位点敏感探针的氯化锌（ZnCl2）等玻璃形成物进行超淬火。含复合离子的玻璃形成物的超淬火将允许在最近的一篇论文中描述的第二有效温度的定义。2004年开始，通过“压力调整”和（ii）机械损伤获得的新玻璃。压力淬火和损伤形成的玻璃将作为超淬火玻璃的类似物进行检查。此外，它还显示了如何在比通常的玻璃成型机更复杂的系统中，超淬火可以为复杂过程的详细研究打开大门。这可能是(i)可以在发生之前淬灭的液-液相变，然后在再加热时空闲地研究，或（ii）分子结构变化，例如蛋白质的折叠，或某些化学排序过程的进展。在每种情况下，都给出了原理的初步证明。使用在本资助期内发表的论文。本文概述了玻璃成形实验研究的一些新的出发点，并提出了实现这些研究的资源要求。该小组以前的工作主要集中在亚稳态平衡中的液体，或者使用类似的时间尺度进行冷却和加热，从液体到玻璃再到液体的转变。这种新方法最初是为了与计算机模拟有更大的重叠而设计的，但现在已经被认为是一种探索过冷液体状态和玻璃态动力学的策略。它还受到能量景观上陷阱性质的信息（包括它们的能量学和振动动力学）的激励，这些信息可以通过对超淬火玻璃的询问获得。在美国国家科学基金会的支持下，这位作者刚刚为一本关于药物的书“药物的冷冻干燥”撰写了一篇关于玻璃态基本方面的文章，因为现在许多药物都是通过冷冻干燥过程保存在玻璃态的。选择这种材料的原因之一是玻璃体材料比它们的晶体类似物溶解得快得多（比如在胃里）。研究玻璃的热力学和动力学性质对药物加工的发展具有重要意义。这个关于分离超淬火的物理和化学效应的项目将为研究生和本科生的研究人员提供有价值的培训。

This project aims to study glasses that are formed on extremely short time scales by "hyperquenching." Developed over decades to vitrify "bad" glassformers, hyperquenching has never been systematically applied to explore the high temperature structure and properties of common glassformers. The possibility of examining features of glassforming liquids in the absence of smearing by vibrational excitation is a central goal for this study. Some key results were obtained in the previous grant period supporting the concept of topological defects as elementary excitations in glasses, and experiments needed to properly develop this idea will be performed. Hyperquenching of glassformers like zink chloride (ZnCl2) containing site sensitive probes like cyanide ion CN- will be performed. Hyperquenching of complex ion containing glassformers will permit the definition of the second fictive temperature described in a recent paper. Initiated in 2004 are new glasses obtained by (i) "pressure-tuning" and (ii) mechanical damage. Pressure-quenched and damage-formed glasses will be examined as analogs of hyperquenched glasses. In addition, it is shown how, in systems with additional complexity over the usual glassformer, hyperquenching can open the door to detailed study of the complex process. This may be (i) a liquid-liquid phase change that can be quenched-in before it happens, and then studied at leisure during reheating, or (ii) a molecular structure change, such as the folding of a protein, or the progress of some chemical ordering process. In each case the preliminary proof of principle is given. using papers published during the present grant period. In this proposal some new points of departure for the experimental study of glassformers are outlined and resources to bring them to fruition are requested. Previous work in this group was focussed on liquids in metastable equilibrium, or on the transition from liquid to glass and back to liquid using similar time scales for cooling and heating. The new approach was originally designed to permit greater overlap with computer simulation, but has now been recognized as a strategy for exploring supercooled liquid states, and glassy state dynamics, in its own right. It is also motivated by the information on the nature of traps on the energy landscape (both their energetics and vibrational dynamics) that can be obtained by interrogation of the hyperquenched glass.%%%Under NSF support this author has just contributed an article on fundamental aspects of the glassy state to a book on Pharmaceuticals "Freeze Drying of Pharmaceuticals" because many of today's drugs are now being preserved in the glassy state by the freeze drying process. One of the reasons for this choice is that vitreous materials dissolve much more rapidly (in the stomach for instance) than do their crystalline analogs. This work on the thermodynamics and dynamic properties of glasses is of fundamental importance to the development of drug processing. This project on separating physical from chemical effects of hyperquenching will provide valuable training to both graduate and undergraduate researchers.