Projects per year
Abstract / Description of output
While ammonia and water readily form hydrogen-bonded molecular mixtures at ambient conditions, their miscibility under pressure is not well understood, yet crucial e.g. to model the interior of icy planets. We report here on the behaviour of ammonia-water mixtures under extreme pressure conditions, based on _rst-principles calculations of 15 stoichiometries in the pressure range of 1 atm to 10 Mbar. We show that compression facilitates proton transfer from water to ammonia in all relevant mixtures. This favors ammonia-rich hydrates above 1 Mbar, stabilized by complete de-protonation of water and the formation of the unusual structural motifs O2􀀀_(NH+4)2 and O2􀀀_(N2H+7)2. The hydronitrogen cations persist to the highest pressures studied. We predict a new ammonia-rich 4:1-hydrate at intermediate pressures and _nd that by 5.5 Mbar, close to the core-mantle boundary of Neptune, all cold ammonia-water mixtures are unstable against decomposition into their constituents.
Original language | English |
---|---|
Article number | 234501 |
Journal | The Journal of Chemical Physics |
Volume | 149 |
Early online date | 17 Dec 2018 |
DOIs | |
Publication status | E-pub ahead of print - 17 Dec 2018 |
Fingerprint
Dive into the research topics of 'Novel phases in ammonia-water mixtures under pressure'. Together they form a unique fingerprint.Projects
- 2 Finished
-
RPhase diagrams of mixed molecular clathrates and hydrates from first-principles calculations
1/11/15 → 31/10/16
Project: Research
Datasets
-
Novel phases in ammonia-water mixtures under pressure
Hermann, A. (Creator), Edinburgh DataShare, 10 Dec 2018
DOI: 10.7488/ds/2473
Dataset