Non-equilibrium heat flow over patterned interfaces (Ref. 4659)

当电池充电时，离子移动到电极中的过程导致发热。该区域在系统中创建了热导率显著变化的边界。边界上的热流是一个非常复杂的问题，既涉及宏观尺度和微观尺度的现象，也涉及大量的非平衡物理。这是进一步恶化的困难实验产生完美或无缺陷的接口。在过去的十年中，声子输运已经通过第一原理Peierls-Boltzmann输运方法的发展而发生了革命性的变化，该方法能够在不需要可调参数的情况下预测材料的热性质[1]。然而，这些方法受到其规模和对高功率计算资源（超级计算机）的需求的高度限制。最近，Hepplestone博士已经表明，可以操纵2D结构的界面来创建电流和掺杂[2]。早期界面散射理论[3，4]和从头计算的结合表明，离子嵌入界面有望提供独特的方式来操纵热传输。原则上，嵌入引入了所谓的振子，其强烈地散射声子，从而降低了热导率。这反过来又提供了创建热开关以及通过防止热级联来增强电池性能的机会。在宏观尺度和微观尺度上理解这一挑战的物理学是一个巨大而令人兴奋的理论问题。该项目可以分为四个阶段：第一阶段该项目的初始重点是已知界面的导热性。使用第一原理理论和经验模型，电导率将被评估。通过直接比较插层和非界面的性质，旨在量化插层在改变热导率方面的作用，从而量化这些影响的程度。评估需要三个阶段，第一是使用冻结声子技术计算声子能带结构，以及非谐力常数。在评估了这些术语之后，有必要考虑不同散射机制的作用，同时量化界面杂质的作用。最后，从这个，然后可以评估导电性。第二阶段在第二阶段，需要一个大规模的有限差分热流模拟器，以考虑和模拟基于傅立叶-卡塔内奥热定律的非均匀温度分布的影响。这将允许考虑非常复杂的几何形状，而不需要微观模拟。在这种有效介质方法中，我们将能够精确地探索热流在各种几何形状和界面上的不均匀程度，并研究在什么条件下界面上的平衡传输原理成立。这种方法将使我们能够模拟多个尺度（100 nm+），并推动模型检查其故障以及如何增强这样的系统。第3阶段第1阶段中讨论的方法依赖于单模弛豫时间方法的假设。实际上，这种方法假设系统中的其他载流子仍然服从玻色爱因斯坦分布函数，并且只有散射声子模式导致分布函数被干扰或改变。根据探索第2阶段获得的信息，它的目的是探索整个界面的非平衡功能的作用，开发一种新的理论来模拟这种制度，建立在第一原理的基础上，用于批量开发这种非平衡系统的新方法。

When a battery charges, the process of ions moving into the electrode results in heat generation. This region creates a boundary in the system where the thermal conductivity varies dramatically. Heat flow over boundaries is a very complicated problem, with both macroscale and microscale phenomena being involved as well as substantial non-equilibrium physics. This is further exasperated by the difficulty experimentally in producing perfect or defect free interfaces. In the past decade, phonon transport has been revolutionised by the development of first principles Peierls-Boltzmann transport approaches, capable of predicting the thermal properties of materials without the need for adjustable parameters [1]. However, these approaches are highly limited by their scale and the need for high powered computing resources (supercomputers). Recently, Dr. Hepplestone has shown that interfaces for 2D structures can be manipulated to create current flow and doping [2]. The combination of early interface scattering theory [3,4] and ab initio calculations has shown that the intercalation of ions into interfaces promise to provide unique ways to manipulate thermal transport. The intercalation introduces, in principle, what are known as rattlers, which scatter phonons strongly, thus reducing the thermal conductivity. This in turn presents the opportunity to create thermal switches as well as enhance battery performance by preventing thermal cascades. Understanding the physics of this challenge at both the macroscale and the microscale is a vast and exciting theoretical problem. This project can be broken down in four phases:Phase 1 The initial focus of the project would be on thermal conductivity of known interfaces. Using first principles theory and empirical models, the conductivity will be evaluated. By directly comparing the properties of a intercalated and non-interfaces, it is intended to quantify the role of intercalation in changing the thermal conductivity, and thus quantify how much these effect it. Three stages of evaluation are necessary, the first is to calculate the phonon band structures, using the frozen phonon technique, as well as the anharmonic force constants. Having evaluated these terms, it is then necessary to consider the role of differing scattering mechanisms, whilst quantifying the role of interface impurities. Finally, from this, one can then evaluate the conductivity. Phase 2 In phase two a large scale finite difference heat flow simulator will be needed, to consider and model the effects of non uniform temperature distributions based upon Fourier-Cattaneo heat law. This will allow very complicated geometries to be considered, without the need for microscopic simulation. In this effective medium approach, we will be able to explore precisely how non-uniform the heat flow is across various geometries and interfaces and examine under what conditions the principle of an equilibrium transport across an interface holds. This approach will allow us to model multiple scales (100 nm+) and push the model to examine its breakdown and how such a system can be enhanced.Phase 3The approach discussed in Phase 1 relies on the assumption of the single mode relaxation time method. Effectively, this approach assumes that other carriers in the system still obey the Bose Einstein Distribution function, and only the scattering phonon mode results in a disturbed or changed distribution function. Based upon the information gained by exploring phase 2, it is intended to explore the role of non-equilibrium functions across the interface, developing a new theory to model this regime, building upon the first principles works used in bulk to develop a new approach for such non-equilibrium systems.