Phase transition and superconductivity of selenium under pressure

In spite of a substantial amount of research has been conducted to unravel the structural configurations of selenium under pressure, the exquisite sensitivity of seleni-um's p-orbital electrons to this external force, leading to a plethora of structural varia-tions, leaves several intermediary phases still shrouded in mystery. We, herein, systemat-ically identify the structural and electronic transformations of selenium under high pres-sure up to 300 GPa, employing crystal structure prediction in conjunction with first-principles calculations. Our results for the transition sequence (P3121→C2/m→R3(_)m→Im3(_)m) of selenium are in good agreement with experimental ones. In particular, we first clarified the knowledge pertaining to the atomic arrangement within the monoclinic C2/m phase of selenium. Electron-phonon coupling calculations indicate that the super-conductivity observed in this material, akin to that in Tellurium, is realized via a phase transition. Furthermore, the superconducting critical temperature (Tc) displays a con-sistent rise as the material experiences high-pressure phase transitions from C2/m to R3(_)m and then to Im3(_)m, achieving a maximum Tc of 13.06 K in the Im3(_)m phase at 97.5 GPa. Our findings illuminate the path towards a deeper comprehension of the high-pressure structure and physics of selenium, prompting the need for innovative experi-mental and theoretical research.