Phase Transition in Fluid Hydrogen at Room Temperature

Abstract

The presence of phase-transition in hydrogen (H 2 ) at around 560 megapascal (MPa) and room temperature was clari ed by Raman and x-ray diffraction studies on both pure H 2 and graphite-H 2 mixture. H 2 is intercalated into the nano-space of graphite, which lowers the transition pressure and temporally expands the size of the honeycomb lattice of graphite under pressure up to 600 MPa. It is supposed that is caused by a gas-liquid phase-transition. According to the peak analysis for Q 1 (J) mode, the ortho-para conversion of H 2 gradually begins to appear after the phase-transition pressure even at room temperature, while peak separation is di cult to achieve under pressure above 1.6 gigapascal (GPa) because of signi cant overlapping of the peak intensities. Because we have missed the ortho-para conversion which could be observed in only such a small pressure range, the uid phase at room temperature was full of mystery.