Ionic phases of ammonia-rich hydrate discovered at high densities

A research team has studied the spontaneous ionization of ammonia hemihydrate (AHH) under compression and discovered ionic phases of ammonia-rich hydrate at high densities.
The team was consisted of researchers from the Hefei Institute of Solid-state Âé¶¹ÒùÔºics (ISSP) of the Hefei Institutes of Âé¶¹ÒùÔºical Science (HFIPS), University of Edinburgh, and the Center for High Pressure Science & Technology Advanced Research and the results of this study were recently published in Âé¶¹ÒùÔºical Review Letters.
Mixtures of ammonia and water are major components of the "hot ice" mantle regions of icy planets. AHH plays a pivotal role as it precipitates from water-rich mixtures under pressure.
The team compressed an exemplary ammonia-water compound to over 1.2 million atmospheres, corresponding to a depth of about 9,870/8,085 kilometers inside Uranus/Neptune, and tracked its structural and dynamical properties. The calculations demonstrated that the compressed mixture transforms into a very stable ammonium oxide, (NH4+)2O2-.
The presence of such a stable ionic compound deep inside icy planets will influence our understanding about such planets' formation and evolution to the present day. These intriguing ionic phases can exist over a considerably wide pressure region hence greatly extend the phase diagram of AHH.
More information: Wan Xu et al. Ionic Phases of Ammonia-Rich Hydrate at High Densities, Âé¶¹ÒùÔºical Review Letters (2021).
Journal information: Âé¶¹ÒùÔºical Review Letters
Provided by Chinese Academy of Sciences