Collaborative Research: CSEDI--First Principles Calculations and Measurements of Thermal Diffusivity for Application to the Earth's Interior

地球，就像任何其他温暖的物体一样，通过将热量散发到周围环境中来冷却。速率限制步骤是热量从较热的内部传递到表面，在那里热量释放表现在火山和地壳和岩石圈板块的运动中，这反过来又会产生地震。这些近地表现象影响生物圈和人类的努力，因此了解驱动它们的内部热源是很重要的。 内部的冷却由矿物和岩石的物理性质决定，其中最重要的是热扩散率和传导率。激光闪光分析（LFA）技术从材料科学的最新转移，现在允许精确测量地质材料的热输运性质。 然而，对地球内部的研究需要实验无法获得的条件下的数据，例如，T 2300 K和P 100 GPa。 因此，需要一个强大的理论模型来推断实验室数据中的趋势，以适应地球的条件。 模型是可用的，但有严重的缺陷，包括根据包含重大和系统性错误的旧数据进行基准测试。这一建议涉及一个大大改进的强大的理论模型的发展，并提供准确的，国家的最先进的测量热扩散率对该模型可以进行基准。该研究对于理解岩石圈最外层和金属核与岩石地幔之间的内部边界的传导、内部的地幔环流以及由于守恒方程中的非线性反馈引起的行星体的热演化具有重要意义。 这项工作不仅将进一步加深我们对行星尺度过程的理解，而且还将探索热传输的微观起源。特别是，较旧的方法，包括与热电偶的物理接触，在298 K附近低估了热扩散率（D）约25%，并且提供了错误的D/T符号和量值。 许多模型都是基于导热系数（* =*CPD，其中 是密度，CP是热容）可以完全从热力学性质获得，热力学性质是静态的，描述了平衡行为，而输运本质上是动态的，涉及振动原子的相互作用，并且发生在非平衡条件下。因此，我们建议构建一种新型的模型的基础上的计算方法，结合定量的，第一性原理计算的振动的动态相互作用的矿物和微观玻尔兹曼运输理论预测稳态非平衡分布和振动能量的变化，并基准此模型对激光闪光测量的简单，但相关的系统。矿物物理组和固体理论组将并行工作，分别建立可靠的实验和理论数据。最初，该研究将集中在简单的系统，计算显然是可行的：Si，NaCl和MgO，随后扩展到Al 2 O3和Mg 2SiO 4。实验工作将集中在将金刚石砧座单元与LFA连接，以提高测量精度 *

The Earth, like any other warm object, cools with time by shedding its heat to the surroundings. The rate limiting step is transfer of heat from inside the hotter interior to the surface, where heat release is manifest in volcanoes and motions of the crustal and lithospheric plates, which in turn generate earthquakes. These near-surface phenomena impact the biosphere and human endeavors and thus understanding the interior heat source that drives them is important. Cooling of the interior is governed by physical properties of minerals and rocks, foremost of which are thermal diffusivity and conductivity. Recent technology transfer of laser-flash analysis (LFA) from materials science now permits accurate measurement of thermal transport properties of geologic materials. However, studies of the Earth's interior require data at conditions not accessible by experiment, e.g., T 2300 K and P 100 GPa. Therefore, a robust theoretical model is needed to extrapolate the trends seen in the laboratory data to conditions in the Earth. Models are available, but have serious flaws, including being benchmarked against old data that contain significant and systematic errors. This proposal concerns development of a much improved robust theoretical model and providing accurate, state-of-the-art measurements of thermal diffusivity against which this model can be benchmarked. The proposed research is important to understand conduction in the outermost lithosphere layers and in the interior boundary between metal core and rock mantle, mantle circulations in the interior, and thermal evolution of planetary bodies due to nonlinear feedback in conservation equations. This work will further our understanding of not only planetary scale processes, but also probes the microscopic origin of heat transport.Specifically, older methods, involving physical contact with thermocouples, underestimate thermal diffusivity (D) by ~25% near 298 K, and provide incorrect signs and magnitude for D/T. Many models are based on the erroneous notion that thermal conductivity (* =*CPD, where is density and CP is heat capacity) can be obtained entirely from thermodynamic properties, which are static and depict equilibrium behavior, whereas transport by it nature is dynamic, involving interactions of vibrating atoms, and occurs under non-equilibrium conditions. We therefore propose construction of a new type of model based on a computational method that combines the quantitative, first-principles calculation of the dynamic interactions of vibrations in the mineral and microscopic Boltzmann transport theory to predict steady-state non-equilibrium distribution and changes in vibrational energy, and to benchmark this model against laser-flash measurements of simple, but relevant, systems. The mineral physics group and the solid-state theory group will work in parallel to establish reliable experimental and theoretical data, respectively. Initially, the study will focus on simple systems for which calculations are clearly feasible: Si, NaCl, and MgO, subsequently expanding to Al2O3 and Mg2SiO4. Experimental efforts will concentrate on interfacing a diamond anvil cell with the LFA to improve accuracy in measuring *