Understanding the physics of the disordered state: universality of phenomena in glasses and resistance to amorphization by radiation damage

无定形固体在技术应用中有着广泛的应用。眼镜是我们日常生活中非常熟悉的物品。然而，与拓扑有序的固体相比，人们在实验和理论上对它们的理解要少得多。在过去的几十年里，实验研究产生了许多新的数据，但对这些数据的理论理解仍然缺乏。通过将观察到的行为与非晶态中的微观过程联系起来，这一提议将促进对非晶态物理学的基本理解。这项提议包括两部分，一是对普遍弛豫现象的微观描述，二是理解抗辐射损伤的非晶化。在过去的三十年里，非晶态固体一直被其驰豫特性的普遍性所吸引，其中许多特性是在晶体中看不到的。这一提议的第一部分旨在从根本上了解非晶态固体中现象的普遍性的起源，这一现象长期以来一直困扰着科学家。我提出了一个一般性的问题，即与无序状态的性质相关的复杂性如何导致观察到的现象的简单性(普遍性)。在无定形固体中有几个主要的普适性类别。在拟议的研究中，将讨论以下问题：(A)玻璃和超冷液体在玻璃化转变时的拉伸指数松弛；(B)刚性渗流点附近的松弛普适性；以及(C)热容量和吸声的低温普适性。我将提供这些现象的微观描述。这里的重点是通过用普遍局部驰豫事件的动力学来描述这些看似不同的驰豫现象。这些事件是玻璃中的基本弛豫量子，它们在微观尺度上驱动着普遍的弛豫现象。粒子辐照是产生无定形固体的方法之一，该提议的第二部分旨在了解是什么使材料通过辐射损伤而非晶化。我对这一领域的兴趣是因为需要安全地封装高放射性核废料和过剩的钚。为什么一些材料很容易被重高能离子非晶化，而另一些材料具有极强的抗性，即使在非常高的辐射剂量下也不会表现出任何结晶性损失？尽管经过了几十年的研究，但抗辐射损伤的非晶化问题并没有得到普遍解决。我将利用我最近提出的原子间相互作用类型，即共价性和电离性，在这一过程中发挥重要作用，研究许多材料抵抗辐射损伤非晶化的共同起源。此外，我还将研究其他因素如何与抵抗非晶化有关。最后，我将试图提供一个定量的微观理论，将材料的微观参数与其抗非晶化能力联系起来。这将允许预测具有高抗非晶化性能的材料。

Amorphous solids are widely used in technological applications. Glasses are very familiar objects to us in our everyday life. However, compared with topologically ordered solids, they are much less understood both experimentally and theoretically. In the last several decades, experimental studies have produced much new data, but the theoretical understanding of this data is still lacking. This proposal will advance fundamental understanding of the physics of the amorphous state, by linking the observed behaviour to microscopic processes in them. The proposal consists of two parts, the microscopic description of universal relaxation phenomena and understanding resistance to amorphization by radiation damage.Over the last three decades, amorphous solids have been fascinating scientists by the universality of their relaxation properties, many of which are not seen in crystals. The first part of this proposal is aimed at obtaining fundamental understanding of the origin of universality of phenomena in amorphous solids, which has long puzzled scientists. I formulate a general question of how the complexity related to the nature of disordered state gives rise to the simplicity (universality) of the observed phenomena. There are several main universality classes in amorphous solids. In the proposed research, the following will be addressed: (a) stretched-exponential relaxation in glasses and supecooled liquids at glass transition; (b) universality of relaxation around the rigidity percolation point; and (c) low-temperature universality of heat capacity and sound absorbtion. I will provide the microscopic description of these phenomena. The important point here is to relate these seemingly different relaxation phenomena, by describing them in terms of the dynamics of universal local relaxation events. These events are the elementary relaxation quanta in glasses which drive the universal relaxationphenomena at the microscopic scale.Particle irradiation is one of the ways of producing amorphous solids, and the second part of this proposal is aimed at understanding what makes a material amorphizable by radiation damage. My interest in this area is stimulated by the need to safely encapsulate highly radioactive nuclear waste and surplus Pu. Why some materials are readily amorphized by heavy energetic ions, whereas others are extremely resistant and do not show any loss of crystallinity even at very high radiation doses? Despite decades of research, the problem of resistance to amorphization by radiation damage is not generally solved. I will investigate the common origin of resistance to amorphization by radiation damage in many materials, using my recent proposal that the type of interatomic interactions, covalency and ionicity, plays an important role in this process. In addition, I will investigate how other factors may be relevant for resistance to amorphization. Finally, I will seek to provide a quantitative microscopic theory that links the microscopic parameters of a material to its resistance to amorphization. This will allow to predict materials with high resistance to amorphization.