Face-Centered Cubic Platinum Hydride and Phase Diagram of PtH

Recent research on superconductivity of high-pressure hydrides generated many phase stability calculations with a lack of their experimental verification; a typical example is Pt–H system. The stability of eight PtH structures was predicted, while the experiments revealed the existence of only hexagonal close-packed (hcp) and trigonal PtH. Face-centered cubic (fcc) PtH was predicted to be nearly isoentalpic to the hcp PtH and stable near 100 GPa, but never observed experimentally. Here we report the first synthesis of the fcc PtH using laser-heated diamond anvil cell. It was found to occupy a high-temperature area of the phase diagram in a wide pressure range of 20–100 GPa, being metastable at room temperature. Our results look promising for uncovering weak approximations in current high-pressure hydrides stability ab initio calculations.