Prediction of stoichiometric PoHn compounds: crystal structures and properties

Abstract

Stable compounds, crystal structures and properties 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, PoH₂, PoH₄ and PoH₆) are predicted to be stabilized in an excess hydrogen environment. Except for PoH, other stable stoichiometries exhibit intriguing structural character with the appearance of H₂ units. Moreover, the electronic band structure and 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 PoH₄ is a superconductor with a critical temperature T_c of 41.2–47.2 K at 200 GPa.