Speaker
Description
Recent extensive research on high-temperature superconductivity in compressed binary hydrogen-rich compounds generat-ed a large corpus of phase stability calculations with an evident lack of their experimental verification. Pt-H system at high pressure represent a typical example of inconsistency between computational approach, which predicted stability of eight PtH structures, and experiments revealing the existence of only two modifications: hexagonal close-packed (hcp) PtH (alt-hough at drastically lower pressures than predicted), and trigonal PtH (not foreseen by ab initio calculations). Of particular interest is face-centered cubic (fcc) platinum hydride - a product of hydrogen intercalation into the native structure of fcc Pt. This phase was predicted to be nearly isoentalpic to the hcp PtH and stable between 93 and 105 GPa, but has been never observed experimentally. Here we report the first synthesis of the fcc PtH using laser heated diamond anvil cell. The fcc plat-inum hydride was found to occupy high-temperature area of the phase diagram in a wide pressure range of 20 – 100 GPa. It can be quenched, although with partial transformation into the hcp phase, thus being metastable at room temperature. Our results look promising for uncovering weak approximations in current ab initio approaches, used for computational model-ling of high-pressure hydrides stability. Moreover, here we clarify the view on the inertness of Pt as a heat absorber in laser-heating high-pressure experiments with hydrogen-containing systems.The research was carried out at PETRA III (DESY), Р02.2 Extreme conditions beamline, proposal #I-20180048.
This work was supported by RFBR grant №18-35-20047.
