Phase diagram and superconductivity of polonium hydrides under high pressure

Abstract

High pressure structures, phase diagram and superconductivity of polonium hydrides have been systematically investigated through the first-principles calculations based on the density functional theory. With the increasing pressure, several stoichiometries (PoH, ${\text{PoH}}_{\text{2}}$, ${\text{PoH}}_4$ and ${\text{PoH}}_6$) are predicted to stabilize in the excess hydrogen environment. All of the reported hydrides, exception of PoH, exhibit intriguing structural character with the appearing ${\text{H}}_2$ units. Moreover, our electronic band structure and the projected density of states (PDOS) demonstrate that these energetically stable phases are metallic. The application of the Allen-Dynes modified McMillan equation with the calculated electron-phonon coupling parameter reveals that ${\text{PoH}}_4$ is a superconductor with a critical temperature $T_c$ of 41.2-47.2 K at 300 GPa.

14 pages, 5 figures