电子衍射中原子对分布函数的自动提取及其定量分析在功能材料中的应用

Local structure (including short-range order and intermediate-range order) is a key factor to the properties of materials, quantitative analysis of atomic pair distribution function based on the total scattering theory both including Bragg scattering and diffusing scattering signals has been developed in the X-ray and neutron diffraction, and it has been becoming a powerful tools to determine the local structure. In this projection we will explore an electron diffraction analysis tools based on the X-ray total scattering theory to automatically extract atomic pair distribution from electron diffraction pattern, the core modules of the package should be included: intensity profile of 2D electron diffraction pattern→calculation of scattering curve→reduced interference profile→reduced pair distribution function. Furthermore, in order to solve the quantitative problem we will quantitatively analyze atomic pair distribution function of Bi2WO6 nanosheets to study its dynamical decomposition under the electron-beam irradiation, as well as the correlation between local structure and superconductivity of iron-based superconductors before and after the chemical dopping.

以短程序和中程序为主的局域结构是影响材料物理化学性能的关键因素，基于总散射理论(布拉格散射和弥散散射)的原子对分布函数的定量分析已在X-射线和中子衍射中逐渐兴起，成为材料局域结构分析最为有效的分析技术之一。本项目拟将X-射线总散射分析技术进一步拓展到电子衍射中，通过计算机编程自动校正电子衍射的动力学效应，开发出从电子衍射自动提取原子对分布函数的软件包。为了给出基于电子衍射的原子对分布函数定量分析的解决方案，该项目还将利用原子对分布函数定量研究铁基超导体在化学掺杂前后局域结构与超导电性的关联问题，以及Bi2WO6光催化材料在电子束辐照下原子尺度的动态分解过程。

原子的局域结构是影响材料物理化学性能的关键因素，但常规的X射线衍射仪仅能得到较窄衍射角范围内的平均衍射信息，不适合原子对分布函数的分析。本项目基于总散射理论，实现了从电子衍射花样中自动提取原子对分布函数的功能，开发了相关分析软件包ePDF Tools，系统研究了电子衍射的实验变量、分析变量对原子对分布函数的影响；利用原子对分布函数技术研究了二氧化钛在从锐钛矿相到金红石相的结构相变过程中TiO6八面体的局域结构变化特征，以及电子束辐照下Bi2WO6的动态分解过程。从电子衍射花样中迅速提取可定量分析的原子对分布函数，是对透射电子显微镜功能的有效拓展，将有助于原位研究材料的化学反应、结晶或重结晶等动态过程。