University of Glasgow - Equipment Account

液态水和过冷水的特殊行为至少236年来一直困扰着科学，今天仍然被视为化学面临的主要挑战(Whiteside&Deutch，自然，469，21(2011))。在20世纪70年代和90年代，有人认为这种奇怪的行为可能是由热力学转变引起的，甚至可能是第二个临界点。第二个临界点将终止低密度和高密度无定形水相之间的共存线。不幸的是，第二个临界点(如果存在)和相关的多相液-液转变很难研究，因为它被认为低于被称为“无人区”的区域的均匀成核温度(Angell，Science 319,582(2008))。最近的研究，特别是东京大学的Hajime Tanaka(见《自然通讯》1，16(2010))表明，第二个临界点和相关的液-液转变可能更为常见。事实上，现在已经在一系列高度相互作用的原子液体中观察到液-液转变，例如磷、镓、硅、锗和铋，甚至在过冷的Y_2O_3-Al_2O_3中。理论考虑(由Hajime Tanaka和Eugene Stanley小组独立完成)表明，即使在分子液体中，液-液转变也应该是非常常见的。然而，这种转变现在唯一被很好地建立起来的分子液体是亚磷酸三苯酯，田中已经研究过它。不幸的是，只有当液体处于深度过冷和极粘性时，才能观察到这种效果。这排除了对这一现象的详细和明确的研究，并导致了相当大的争议。在初步工作中，我们发现在熔点以上的几种简单的有机液体中存在液-液转变，那里的粘度很低。这将允许对液-液转变进行一系列独特的全面研究，包括在转变过程中重复热循环。将使用一些实验技术，提供从飞秒到千秒的动力学以及从分子到宏观尺度的结构。光谱成像技术将用于深入了解分子相互作用和分子尺度环境及其与液-液转变的关联。这将允许与理论模型进行详细的比较，并将前所未有地深入了解这些现象的物理根源，并允许在未来的应用中进行操纵和控制。为了确保实验工作的最大影响，与LLTS理论和模拟方面的专家保持密切联系至关重要，我们已经获得了H.Eugene Stanley的合作。

The peculiar behaviour of liquid and supercooled water has been baffling science for at least 236 years and is still seen as a major challenge facing chemistry today (Whitesides & Deutch, Nature 469, 21 (2011)). In the 1970s and 1990s, it was suggested that such strange behaviour might be caused by thermodynamic transitions, possibly even a second critical point. This second critical point would terminate a coexistence line between low- and high-density amorphous phases of water. Unfortunately, this second critical point (if it exists) and the associated polyamorphic liquid-liquid transition is difficult to study as it is thought to lie below the homogeneous nucleation temperature in a region known as "no man's land" (Angell, Science 319, 582 (2008)). Recent work, notably by Hajime Tanaka of the University of Tokyo (see, for example, Nature Communications 1, 16 (2010)) has suggested that such a second critical point and the associated liquid-liquid transition might be much more common. In fact, liquid-liquid transitions have now been observed in a range of highly interacting atomic liquids such as phosphorus, gallium, silicon, germanium, and bismuth, and even in supercooled Y2O3-Al2O3. Theoretical considerations (independently by the groups of Hajime Tanaka and Eugene Stanley) suggest that liquid-liquid transitions should be very common even in molecular liquids. However, the only molecular liquid in which such a transition is now well established is triphenyl phosphite, which has been studied by Tanaka. Unfortunately, the effect is only observed when the liquid is deeply supercooled and extremely viscous. This precludes a detailed and definitive study of the phenomenon and has led to considerable controversy.In preliminary work, we have discovered the presence of a liquid-liquid transition in a few simple organic liquids above their melting point where the viscosity is low. This will allow a unique series of comprehensive studies of the liquid-liquid transition involving repeated thermal cycling through the transition. A number of experimental techniques will be used providing access to dynamics from femtosecond to kiloseconds and structure from molecular to macroscopic scales. Spectroscopic imaging techniques will be used to provide insight into molecular interactions and molecular-scale environments and their association with the liquid-liquid transition. This will allow detailed comparison with theoretical models and will give unprecedented insight into the physical origin of these phenomena and allow manipulation and control in future applications. To ensure maximum impact of the experimental work, it is critical to have strong ties with experts in the theory and simulation of LLTs and we have secured the collaboration of H. Eugene Stanley.