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Melting curve and phase diagram of ammonia monohydrate at high pressure and temperature

Melting curve and phase diagram of ammonia monohydrate at high pressure and temperature

Authors :
Mohamed Mezouar
Keevin Béneut
Frédéric Datchi
Haiwa Zhang
L. Andriambariarijaona
Guozhao Zhang
Jean-Antoine Queyroux
S. Ninet
Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC)
Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
State key laboratory of superhard Materials
European Synchrotron Radiation Facility (ESRF)
ANR-15-CE30-0008,SUPER-ICES,Phases superioniques, ioniques et symétriques dans les mélanges de glace (H2O, NH3, CH4) sous conditions extrêmes(2015)
Source :
Journal of Chemical Physics, Journal of Chemical Physics, 2020, 153 (15), pp.154503. ⟨10.1063/5.0021207⟩, Journal of Chemical Physics, American Institute of Physics, 2020, 153 (15), pp.154503. ⟨10.1063/5.0021207⟩
Publication Year :
2020
Publisher :
HAL CCSD, 2020.

Abstract

International audience; The phase diagram and melting behavior of the equimolar water-ammonia mixture have been investigated by Raman spectroscopy, x-ray diffraction, and visual observations from 295 K to 675 K and up to 9 GPa. Our results show non-congruent melting behavior of ammonia monohydrate (AMH) solid below 324 K and congruent melting at higher temperatures. The congruent melting is associated with the stability of a previously unobserved solid phase of AMH, which we named AMH-VII. Another, presumably water-rich, hydrate has also been detected in the range 4 GPa-7 GPa at 295 K on decompression of the high pressure disordered ionico-molecular alloy (DIMA) phase. Comparing our melting data to the literature suggests that non-congruent melting extends from 220 K to 324 K and that the solid phase that borders the fluid between 220 K and 270 K, called AMH-III, is not a proper phase of AMH but a solid solution of ammonia hemihydrate and ice. These results allow us to propose a revised and extended experimental phase diagram of AMH. Published under license by AIP Publishing. https://doi.org/10.1063/5.0021207 ., s

Details

Language :
English
ISSN :
00219606 and 10897690
Database :
OpenAIRE
Journal :
Journal of Chemical Physics, Journal of Chemical Physics, 2020, 153 (15), pp.154503. ⟨10.1063/5.0021207⟩, Journal of Chemical Physics, American Institute of Physics, 2020, 153 (15), pp.154503. ⟨10.1063/5.0021207⟩
Accession number :
edsair.doi.dedup.....b995183fa806cbce5d82fa07f636f68e
Full Text :
https://doi.org/10.1063/5.0021207⟩