Structures and Properties of Osmium Hydrides under Pressure from First Principle Calculation

The pressure-induced new structures and properties of osmium hydrides were systematically explored in a wide pressure range 0-300 GPa using ab initio methods. Three stable stoichiometries, that is, OsH, OsH3, and OsH6, are predicted above 50 GPa. The above hydrides exhibit metallic character with the notable band structures exception of OsH6. It is interesting to note that the phase P2(1)/c of hydrogen-rich OsH6 adopts intriguing structures with H-2 units. The electron-phonon coupling calculations indicate that the superconducting critical temperature (T-c) values of Fm-3m-OsH is 2.1 K at 100 GPa. Comparing to pure Os, the addition of hydrogen is in favor of improving the superconducting temperature.