三维拓扑绝缘体Bi2Se3、Bi2Te3和Sb2Te3是近些年来发现的一种全新的量子物质态。由于其能带结构拓扑性质与传统意义下绝缘体的不同，表现出受时间反演对称性保护的表面金属态等特殊性质。而在高压下，该体系也表现出诸如压力诱导超导电性、半导体-金属转变和电子拓扑转变等物理现象，与此相关的高压下结构及其变化规律这一基本问题也得到了应有的关注。本项目拟采用高压XAFS谱和高压XRD等实验手段，结合XANES谱多重散射从头计算和第一性原理计算等理论工具，系统研究三维拓扑绝缘体Bi2Se3等体系高压诱导结构相变等问题。从高压XAFS短程序结构视角分析该体系高压诱导结构相变的路径、高压相结构、混合占位、高压相电荷转移和压力诱导电子拓扑转变的局域结构机制等，与高压XRD等提供的长程序结构信息结合，明确该体系高压诱导结构相变若干争议，为理解该体系高压诱导出现的丰富物理现象提供晶体结构基础。

Three-dimensional topological insulators (3D-TIs) Bi2Se3、Bi2Te3 and Sb2Te3 are new quantum matter discovered in recent years, and their surfaces exhibit the feature metallic surface states topologically protected against scattering by time-reversal symmetry due to topologically nontrivial band structure. Under high pressure, some new pressure-induced features , such as superconductivity, semiconductor-metal phase transition and electronic topological transition, are gradually revealed in this 3D-TIs. Their pressure-induced structural phase transitions have also attracted extensive attention. This project intends, using the high-pressure X-ray absorption spectroscopy (XAFS) and X-ray diffraction (XRD) measurements, combined with multiple scattering ab initio calculation and first principle calculation, etc., to investigate systematically the pressure-induced structural phase transition and related problems. The high-pressure XAFS spectroscopy, combined with high-pressure XRD, will be performed on 3D-TIs to explore the pressure-induced crystal structural evolutions, phase structure under high pressure, disordered array of atoms in the crystal lattice, pressure-induced charge transfer and electronic topological transition. We will clarify the argument about pressure-induced structural phase transition of 3D-TIs. The results will provide a new perspective to understand deeply the crystal structure under high pressure and the relationship with the abundant physical phenomena induced by high pressure in 3D-TIs.