无序合金的高温高压结构理论及其在地核物质"Fe-Si/S"中的应用

当代物理学对非晶体材料的结构学研究尚处于起步阶段，研究往往需要借助简化的理论模型及经验的模拟方法。在极端条件下（高压/温），由于电子结构的突变，传统的物质认知经常会遇到理论上的局限，因此我们必须从全新的视角出发，构建新的理论体系。籍此，我们将结合前沿的理论手段及先进的实验方法，研究无序材料尤其是替代合金在高压条件下的性质，期以得到对物质结构及稳定性在更深层次上的理解。我们计划使用高分辨同步辐射XRD技术结合最大熵方法来研究物质在高压条件下的电子拓扑结构，并运用分子动力学模拟电子结构计算，以及准随机近似等理论方法探索材料的宏观性质。我们研究目标是在原子尺度上发展一个新的，无参量的理论模型，用于描述和预测合金的物理化学性质。该技术将被用于一个非常重要的，尚未解决的地学问题，那就是解释铁的单质和化合物在地核中的构成，这对我们理解地球的起源、演化等重大问题具有极为重要的意义。

It is fair to assume that the basic structural principles of crystalline materials under normal conditions have now been established. In contrast, for disordered solids, most often, one must rely on empirical rules or simple theoretical models. Pressure is a convenient and powerful thermodynamics parameter to alter the electronic structure of a material. Under extreme conditions, the traditional paradigm may not be extrapolated to disorder materials. Here, we proposed a research program to gain insight on the fundamental principles underlying the structure and stability of disordered solids under high pressure, with a focus on crystalline substitutional alloys. We will make use of high resolution synchrotron x-ray powder diffraction to extract the electron topology using the maximum entropy method. This is complement with static and dynamics first-principles electronic structure calculations on disordered models generated from special quasirandom-structures. The goal is to develop an atomistic and parameter free model to describe and predict the properties of the alloys. The technique will be applied to the study on one of the most important substitutional alloys, the iron-light element compound under the deep Earth conditions. We anticipate the results are importance for future developments in solid state physics and materials science. .