Neutron diffraction study on ice VII at high pressure and high temperature

Sano, Asami   ; Kobayashi, Hiroki*; Komatsu, Kazuki*; Kagi, Hiroyuki*; Ohira, Itaru*; Kakizawa, Sho*

Ice is a key component of icy planets and moons, and its behavior at high pressure and high temperature is crucial for understanding planetary interiors. Under such conditions, hydrogen mobility increases, and superionic ice phases have been predicted, where hydrogen diffuses through a static oxygen lattice. Previous X-ray studies suggested a first-order transition of ice VII at pressures above 15 GPa and around 900-1000 K. In this study, we carried out in-situ high-pressure and high-temperature neutron diffraction experiments at PLANET, J-PARC, using the multi-anvil press ATSUHIME' with DO samples. Measurements were performed up to 20 GPa and high temperatures. Structural changes consistent with earlier predictions were observed, though the stability field and detailed behavior appear to differ somewhat from previous reports. A more comprehensive analysis will be presented at the conference.