Deep-Glassy Ice VI Revealed with a Combination of Neutron Spectroscopy and Diffraction

Rosu-Finsen, Alexander; Amon, Alfred; Armstrong, Jeff; Fernandez-Alonso, Félix; Salzmann, Christoph G.

doi:10.1021/acs.jpclett.0c00125

Cited by 26 publications

(36 citation statements)

References 45 publications

(153 reference statements)

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“…It appears that the timescale for H-ordering and applied cooling rates are very similar to the one in our experiments at 10 GPa and ∼150 K higher temperatures. We therefore expect similar phenomena to exist in the case of the ice VII-VIII transition, such as the existence of "deep glassy states" (27,29) at sufficiently high cooling rates and the presence of a low-temperature endotherm as well as transient-hydrogen ordering upon heating. The remarkable difference is that in ice VII-VIII it would be observable in pure ice and at temperatures close to ambient, although at considerably higher pressures.…”

Section: Runmentioning

confidence: 83%

“…1) situated at [0, 1y(D1), 2 × z(O)z(D1) + 1/4] and constraining the occupancy (occ) of D1 and D2 to occ(D2) = 1occ(D1). Note that this H-disorder model was adopted for the whole pressure range since no evidence for a different kind of ordering like recently discussed in the case of ice VI/XV (26)(27)(28)(29) was found in any diffraction pattern of this study.…”

Section: Significancementioning

confidence: 91%

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Anomalous hydrogen dynamics of the ice VII–VIII transition revealed by high-pressure neutron diffraction

Komatsu

Klotz

Machida

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Above 2 GPa the phase diagram of water simplifies considerably and exhibits only two solid phases up to 60 GPa, ice VII and ice VIII. The two phases are related to each other by hydrogen ordering, with the oxygen sublattice being essentially the same. Here we present neutron diffraction data to 15 GPa which reveal that the rate of hydrogen ordering at the ice VII–VIII transition decreases strongly with pressure to reach timescales of minutes at 10 GPa. Surprisingly, the ordering process becomes more rapid again upon further compression. We show that such an unusual change in transition rate can be explained by a slowing down of the rotational dynamics of water molecules with a simultaneous increase of translational motion of hydrogen under pressure, as previously suspected. The observed cross-over in the hydrogen dynamics in ice is likely the origin of various hitherto unexplained anomalies of ice VII in the 10–15 GPa range reported by Raman spectroscopy, X-ray diffraction, and proton conductivity.

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Section: Runmentioning

confidence: 83%

Section: Significancementioning

confidence: 91%

Anomalous hydrogen dynamics of the ice VII–VIII transition revealed by high-pressure neutron diffraction

Komatsu

Klotz

Machida

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…In the present work we are able to show that a transient, disordered state is encountered as the transition state -called ice VI ‡ . The deep glassy state put forward in earlier work by Rosu-Finsen & Salzmann 26,27 could then be the transiently encountered ice VI ‡ , but not ice XIX. Yamane et al suggest in their work that "it is necessary to investigate whether the decompressed samples retain the crystal structure of ice XIX as well as its crystallinity" and speculate about a transition from ice XIX to a deep glassy state upon decompression 39 .…”

Section: Discussionmentioning

confidence: 85%

“…The lack of an experimental crystal structure for ice β-XV has led to widespread speculations about its nature. Whereas Rosu-Finsen & Salzmann have argued for ice β-XV to be in fact a disordered state, in which the H atoms are immobile, i.e., a deep glassy state 26,27 , some of us have speculated about a crystalline phase with a ferroelectric nature 23 .…”

Section: Introductionmentioning

confidence: 99%

Ice XIX: The second hydrogen-ordered polymorph related to ice VI

Gasser

Thoeny

Fortes

et al. 2020

Preprint

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We here report ex situ calorimetry and high-resolution neutron powder diffraction data of a novel ice polymorph produced at 1.8 GPa and recovered to ambient pressure at 80 K. Ice XIX, previously called ice β-XV by us, is shown to be partially hydrogen-ordered and crystallising in a √2 x √2 × 1 supercell with respect to the parent ice VI phase. Our powder data match two nearly degenerate structural models in space-groups \(P\stackrel{-}{4}\) and Pcc2, in which the water molecules are partially antiferroelectrically ordered. Key to the synthesis of deuterated ice XIX is the use of DCl as dopant and the use of a D2O/H2O mixture, where the small H2O fraction nucleates ice XIX. This provides the basis to study the first order-order transition known in ice physics, from ice XIX to its sibling ice XV at ambient pressure. It proceeds via a transition state, ice VI‡, which contains a disordered H-sublattice, whereas both ice XIX and ice XV are fully crystalline.

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“…[36] The positive volume change enable us to suppress hydrogen ordering at pressures greater than ~1 GPa and to isolate so-called 'deep glassy states' of ice VI. [37,38] In a final step, the ice III sample was compressed to 0.…”

mentioning

confidence: 99%

Observation of the Reversible Ice III to Ice IX Phase Transition by Using Ammonium Fluoride as Anti-Ice II Agent

Salzmann¹,

Sharif²,

Slater³

et al. 2020

Preprint

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Ice III is a hydrogen-disordered phase of ice that is stable between about 0.2 and 0.35 GPa. Upon cooling, it transforms to its hydrogen-ordered counterpart ice IX within the stability region of ice II. Because of this metastability, detailed studies of the ice III to ice IX phase transition have so far not been carried out. Using ammonium fluoride doping to prevent the formation of ice II, we now present a detailed study on this phase transition using in-situ powder neutron diffraction. The a and c lattice constants are found to expand and contract, respectively, upon hydrogen ordering yielding an overall negative volume change. Interestingly, the anisotropy in the lattice constants persists when ice IX is fully formed and negative thermal expansion is observed. Analogous to the isostructural keatite and b-spodumenes, the negative thermal expansion can be explained through the build-up of torsional strain within in the a-b plane as the helical ‘springs’ within the structure expand upon heating. The reversibility of the phase transition was demonstrated for the first time upon heating. The ammonium fluoride doping induces additional residual hydrogen disorder in ice IX and is suggested to be a chemical way for ‘excitation’ of the ice-rules configurational manifold. Compared to ices II and VIII, the induced hydrogen disorder in ice IX is smaller which suggests a higher density of configurational states close to the ground state. This study highlights the importance of dopants for exploring water’s phase diagram and underpins the highly complex solid-state chemistry of ice.

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Deep-Glassy Ice VI Revealed with a Combination of Neutron Spectroscopy and Diffraction

Cited by 26 publications

References 45 publications

Anomalous hydrogen dynamics of the ice VII–VIII transition revealed by high-pressure neutron diffraction

Anomalous hydrogen dynamics of the ice VII–VIII transition revealed by high-pressure neutron diffraction

Ice XIX: The second hydrogen-ordered polymorph related to ice VI

Observation of the Reversible Ice III to Ice IX Phase Transition by Using Ammonium Fluoride as Anti-Ice II Agent

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