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

这个项目的目的是研究在极短的时间尺度上通过“超淬火”形成的玻璃。经过几十年的发展，超淬火被用来玻璃化“糟糕的”玻璃成型器，但从未被系统地应用于探索普通玻璃成型器的高温结构和性能。这项研究的中心目标是在没有振动激励的情况下检查玻璃形成液体的特性的可能性。在之前的授权期内，一些关键的结果支持了拓扑缺陷作为玻璃中的基元激发的概念，并将进行适当地发展这一想法所需的实验。将对含有氰离子CN-等位置敏感探针的氯化锌(Zink Cl2)等玻璃成型剂进行超猝灭。含有络离子的玻璃成型剂的超猝灭将允许在最近的一篇论文中描述第二个虚构温度的定义。2004年开始使用的是通过(I)“压力调谐”和(Ii)机械损坏获得的新玻璃。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，还展示了在比通常的玻璃成型机更复杂的系统中，超淬火如何打开了详细研究复杂过程的大门。这可能是(I)液-液相变化，它可以在发生之前被淬灭，然后在重新加热期间进行空闲的研究，或者(Ii)分子结构的变化，如蛋白质的折叠，或某些化学有序过程的进展。在每种情况下，都给出了初步的原则证明。使用在本赠款期间发表的论文。在这项提案中，概述了玻璃成型器实验研究的一些新的出发点，并要求提供资源使其取得成果。该小组以前的工作集中在处于亚稳态平衡的液体，或从液体到玻璃再到液体的转变，使用类似的冷却和加热时间尺度。这种新方法最初的设计目的是允许与计算机模拟有更大的重叠，但现在已经被认为是探索过冷液态和玻璃态动力学的一种策略。它的动机也是关于能量图景上陷阱的性质的信息(包括它们的能量学和振动动力学)，可以通过询问超淬火玻璃获得。%在NSF的支持下，这位作者刚刚为一本关于制药的书《药品的冷冻干燥》贡献了一篇关于玻璃态基本方面的文章，因为今天的许多药物现在通过冷冻干燥过程保存在玻璃态。这一选择的原因之一是，玻璃体材料(例如在胃中)比它们的晶体类似物溶解得更快。玻璃热力学和动力学性质的研究对药物加工的发展具有重要意义。这项关于分离超淬火的物理和化学影响的项目将为研究生和本科生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.