Water is abundant in natural environments but the form it resides in planetary interiors remains uncertain. We report combined synchrotron X-ray diffraction and optical spectroscopy measurements of H2O in the laser-heated diamond anvil cell up to 150 gigapascals (GPa) and 6500 kelvin (K) that reveal first-order transitions to ices with body-centered cubic (bcc) and face-centered cubic (fcc) oxygen lattices above 900 (1300) K and 20 (29) GPa, respectively. We assigned these structures to theoretically predicted superionic phases based on the distinct density, increased optical conductivity, and greatly decreased enthalpies of fusion. Our measurements address current discrepancies between theoretical predictions and various static/dynamic experiments on the existence and location of melting curve and superionic phase(s) in the pressure-temperature phase diagram indicating a possible presence of the conducting fcc-superionic phase in water-rich giant planets, such as Neptune and Uranus.
Observation of hexagonal close-packed water ice at conditions in ice giant planetary interiors
CEA DAM DIF（法国原子能委员会达姆-迪费中心）；Université Paris-Saclay, CEA, Laboratoire Matière en Conditions Extrêmes（巴黎萨克雷大学、法国原子能委员会极端条件物质实验室）；Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Sorbonne Université, CNRS UMR 7590, MNHN（索邦大学矿物学、材料物理与宇宙化学研究所（IMPMC），CNRS UMR 7590，自然历史博物馆）；European Synchrotron Radiation Facility（欧洲同步辐射装置）
Insight into liquid polymorphism from the complex phase behaviour of a simple model
本文系统地研究了Jagla[E. A. Jagla，Phys.Rev.E63，061501（2001）]，使用嵌套采样和自由能方法的组合。采样显示，Jagla势的相图比以前预期的要丰富得多，我们确定了一个新的晶体结构家族，它在相图中的广阔区域内是稳定的。我们表明，新的熔化线位于比低密度和高密度液相之间的边界，这是以前建议躺在一个稳定的区域，在相当高的温度。新发现的结晶相显示出意想不到的复杂结构特征，其中一些与高压冰VI相相同。
Shizuoka University（静冈大学）；The University of Tokyo（东京大学）；Okayama University（冈山大学）；Hiroshima University（广岛大学）；Japan Synchrotron Radiation Research Institute（日本同步辐射研究所）；Tokyo University of Science（东京理科大学）；Nagoya University（名古屋大学）
