Structure determination of the high-pressure phases of topological insulator Bi_2Se_3 using experiments and calculations

摘要

The pressure-induced phase transition of bismuth selenide (Bi_2Se_3) was investigated by combining theoretical calculations with synchrotron powder X-ray diffraction measurements up to 57.4 GPa. We demonstrated that the ambient-pressure rhombohedral Bi_2Se_3 crystallized into a monoclinic structure with the space group C2/m at 9.1 GPa, and eventually to a body-centered tetragonal structure with the space group I4/mmm at about 27.2 GPa. This behavior was different from the transformation sequences of Bi_2Te_3 and Sb_2Te_3. The stabilities of five structures of Bi_2Se_3 were studied by density functional theory calculations. Furthermore, an unusual irreversible relaxation process was observed. We attempted to make clear the unusual structural behavior of Bi_2Se_3 occurring in the compression process and the relaxation process.