Ionic Phases of Ammonia-Rich Hydrate at High Densities

Wan Xu; Victor Naden Robinson; Xiao Zhang; Hui-Chao Zhang; Mary-Ellen Donnelly; Philip Dalladay-Simpson; Andreas Hermann; Xiao-Di Liu; Eugene Gregoryanz

doi:10.1103/PhysRevLett.126.015702

Ionic Phases of Ammonia-Rich Hydrate at High Densities

Wan Xu, Victor Naden Robinson, Xiao Zhang, Hui-Chao Zhang, Mary-Ellen Donnelly, Philip Dalladay-Simpson, Andreas Hermann, Xiao-Di Liu, Eugene Gregoryanz

School of Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

Abstract

Mixtures of ammonia and water are major components of the “hot ice” mantle regions of icy planets. The ammonia-rich ammonia hemihydrate (AHH) plays a pivotal role as it precipitates from water-rich mixtures under pressure. It has been predicted to form ionic high-pressure structures, with fully disintegrated water molecules. Utilizing Raman spectroscopy measurements up to 123 GPa and first-principles calculations, we report the spontaneous ionization of AHH under compression. Spectroscopic measurements reveal that molecular AHH begins to transform into an ionic state at 26 GPa and then above ∼69 GPa transforms into the fully ionic P¯3m1 phase, AHH-III, characterized as ammonium oxide (NH+4)2O2−.

Original language	English
Article number	015702
Pages (from-to)	1-5
Number of pages	5
Journal	Physical Review Letters
Volume	126
Issue number	1
Early online date	6 Jan 2021
DOIs	https://doi.org/10.1103/PhysRevLett.126.015702
Publication status	Published - 8 Jan 2021

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title = "Ionic Phases of Ammonia-Rich Hydrate at High Densities",

abstract = "Mixtures of ammonia and water are major components of the “hot ice” mantle regions of icy planets. The ammonia-rich ammonia hemihydrate (AHH) plays a pivotal role as it precipitates from water-rich mixtures under pressure. It has been predicted to form ionic high-pressure structures, with fully disintegrated water molecules. Utilizing Raman spectroscopy measurements up to 123 GPa and first-principles calculations, we report the spontaneous ionization of AHH under compression. Spectroscopic measurements reveal that molecular AHH begins to transform into an ionic state at 26 GPa and then above ∼69 GPa transforms into the fully ionic P¯3m1 phase, AHH-III, characterized as ammonium oxide (NH+4)2O2−.",

author = "Wan Xu and Robinson, \{Victor Naden\} and Xiao Zhang and Hui-Chao Zhang and Mary-Ellen Donnelly and Philip Dalladay-Simpson and Andreas Hermann and Xiao-Di Liu and Eugene Gregoryanz",

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AU - Xu, Wan

AU - Robinson, Victor Naden

AU - Zhang, Xiao

AU - Zhang, Hui-Chao

AU - Donnelly, Mary-Ellen

AU - Dalladay-Simpson, Philip

AU - Hermann, Andreas

AU - Liu, Xiao-Di

AU - Gregoryanz, Eugene

PY - 2021/1/8

Y1 - 2021/1/8

N2 - Mixtures of ammonia and water are major components of the “hot ice” mantle regions of icy planets. The ammonia-rich ammonia hemihydrate (AHH) plays a pivotal role as it precipitates from water-rich mixtures under pressure. It has been predicted to form ionic high-pressure structures, with fully disintegrated water molecules. Utilizing Raman spectroscopy measurements up to 123 GPa and first-principles calculations, we report the spontaneous ionization of AHH under compression. Spectroscopic measurements reveal that molecular AHH begins to transform into an ionic state at 26 GPa and then above ∼69 GPa transforms into the fully ionic P¯3m1 phase, AHH-III, characterized as ammonium oxide (NH+4)2O2−.

AB - Mixtures of ammonia and water are major components of the “hot ice” mantle regions of icy planets. The ammonia-rich ammonia hemihydrate (AHH) plays a pivotal role as it precipitates from water-rich mixtures under pressure. It has been predicted to form ionic high-pressure structures, with fully disintegrated water molecules. Utilizing Raman spectroscopy measurements up to 123 GPa and first-principles calculations, we report the spontaneous ionization of AHH under compression. Spectroscopic measurements reveal that molecular AHH begins to transform into an ionic state at 26 GPa and then above ∼69 GPa transforms into the fully ionic P¯3m1 phase, AHH-III, characterized as ammonium oxide (NH+4)2O2−.

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DO - 10.1103/PhysRevLett.126.015702

M3 - Article

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JO - Physical Review Letters

JF - Physical Review Letters

IS - 1

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ER -

Ionic Phases of Ammonia-Rich Hydrate at High Densities

Abstract

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