Origins and Stability of Hydrogen-filled C3 Ice

Gas hydrates, found in pressurized environments like Earth's seabed or icy bodies in our Solar System, are able to efficiently store fuel gases like methane or hydrogen. In the HC-5060 experiment, we discovered a new high-density C3 hydrogen hydrate (H2O·2H2) in temperature-quenched, laser-heated samples at P>40 GPa. This phase has the highest gravimetric hydrogen density (>0.25 kg/L) reported up to date. This proposal aims to systematically investigate its pressure-temperature stability range through in situ laser heating X-ray diffraction experiments. We seek insights into its formation mechanism, whether it results from solid-solid phase transition or direct crystallization from the solution. Understanding this compound's stability, structures, and formation mechanisms is crucial for explaining its role in exoplanetary dynamics, icy body formation, and high-density hydrogen-bearing materials' agglomeration.