Exploring Hydrogen Hydrates at High-Pressure from Large Icy Moons to Ocean-Planets: New Phases and Elastic Properties at Ambient Temperature
Résumé
Hydrogen hydrates, formed from hydrogen and water under high-pressure and low-temperature conditions, present significant implications for both energy storage and planetary science. Hydrogenfilled ices are of particular interest in the context of icy celestial bodies, where extreme conditions favor their formation. This study investigates the complex phase diagram of hydrogen hydrate across a pressure range up to 70 GPa, utilizing angle-resolved neutron and X-ray diffraction techniques. We focus on the behavior of key phases: C1, C2, and C3, highlighting the evolution of their crystallographic structures and elastic properties. Our findings reveal critical insights into phase transitions, structural deformations, and the stability of these hydrates, essential to quantify the role of hydrogen on the thermal state and chemical evolution of water-rich worlds of various sizes. The amount of hydrogen stored in the form of high-pressure hydrogen hydrate in their icy interior may condition their oceanic chemistry and their climate stability.