Structural phase transitions in Bi₂Se₃ under high pressure

Raman spectroscopy and angle dispersive X-ray diffraction (XRD) experiments of bismuth selenide (Bi₂Se₃) have been carried out to pressures of 35.6 and 81.2 GPa, respectively, to explore its pressure-induced phase transformation. The experiments indicate that a progressive structural evolution occurs from an ambient rhombohedra phase (Space group (SG): R-3m) to monoclinic phase (SG: C2/m) and eventually to a high pressure body-centered tetragonal phase (SG: I4/mmm). Evidenced by our XRD data up to 81.2 GPa, the Bi₂Se₃ crystallizes into body-centered tetragonal structures rather than the recently reported disordered body-centered cubic (BCC) phase. Furthermore, first principles theoretical calculations favor the viewpoint that the I4/mmm phase Bi₂Se₃ can be stabilized under high pressure (>30 GPa). Remarkably, the Raman spectra of Bi₂Se₃ from this work (two independent runs) are still Raman active up to ∼35 GPa. It is worthy to note that the disordered BCC phase at 27.8 GPa is not observed here. The remarkable difference in atomic radii of Bi and Se in Bi₂Se₃ may explain why Bi₂Se₃ shows different structural behavior than isocompounds Bi₂Te₃ and Sb₂ Te₃.