Disordered structure of D2O ice VII from i
 n s
 i
 t
 u neutron powder diffraction

Jorgensen, J. D.; Worlton, T.G.

doi:10.1063/1.449867

Cited by 72 publications

(50 citation statements)

References 12 publications

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“…2A), indicating good fits to the conventional model. Moreover, our structural parameters agree well with previously published refinements where the data overlap in pressure (19,24,27). However, above ∼26 GPa, we observed a consistent and significant reduction in the quality of the fits to all datasets for the conventional model (Figs.…”

supporting

confidence: 81%

“…The resulting powder data for samples 1-3 were fitted by Rietveldrefinement (26) using the conventional structure of ice VII (19,24,27) (Fig. 1A).…”

Section: Resultsmentioning

confidence: 99%

“…Atomic positions for each of the models considered are given in Table 1. As has been discussed in several previous studies, the local position of the oxygen atom is displaced off the special site by a small amount δ [determined to be 0.08-0.13 Å in various studies (19,24,27,33)]. The direction of this displacement is contentious, and at least two distinct models (with important consequences for H-bonding) have been proposed and explored with experiment (19,24,27) and theory (33).…”

Section: Methodsmentioning

confidence: 99%

“…1A). A "single-site" model was used for the O atoms (19,24,27), which were fixed on the high-symmetry bcc lattice sites, while the deuterium atoms were distributed over tetrahedral sites about these (see Materials and Methods for details of refinements). Hereafter, this is referred to as the "conventional" model.…”

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confidence: 99%

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Neutron diffraction observations of interstitial protons in dense ice

Guthrie

Boehler

Tulk

et al. 2013

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

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The motif of distinct H 2 O molecules in H-bonded networks is believed to persist up to the densest molecular phase of ice. At even higher pressures, where the molecule dissociates, it is generally assumed that the proton remains localized within these same networks. We report neutron-diffraction measurements on D 2 O that reveal the location of the D atoms directly up to 52 GPa, a pressure regime not previously accessible to this technique. The data show the onset of a structural change at ∼13 GPa and cannot be described by the conventional network structure of ice VII above ∼26 GPa. Our measurements are consistent with substantial deuteron density in the octahedral, interstitial voids of the oxygen lattice. The observation of this "interstitial" ice VII form provides a framework for understanding the evolution of hydrogen bonding in ice that contrasts with the conventional picture. It may also be a precursor for the superionic phase reported at even higher pressure with important consequences for our understanding of dense matter and planetary interiors.crystallography | high pressure | water A ll of the some 16 phases of crystalline ice documented to date exhibit a tetrahedrally coordinated structure in which each molecule is H-bonded to four neighbors in an extended network. Above ∼2 GPa, the phase diagram contains just two, closely related, molecular phases: orientationally disordered ice VII and its ordered low-temperature analog ice VIII (1). Both phases have body-centered, close-packed oxygen sublattices with cubic and tetragonal symmetry, respectively. Infrared spectroscopy has provided evidence for bond symmetrization in ice VII-meaning covalent and H-bonds become geometrically equivalent, and ice becomes a simple oxide-starting around 60 GPa (2-4). Meanwhile, X-ray diffraction indicates the persistence of a closely body-centered cubic (bcc) oxygen sublattice up to at least 210 GPa (5-9). At the highest pressures, this system has been studied extensively by numerous experimental techniques [including infrared (3-4, 10) and Raman spectroscopy (2, 11), Brillouin scattering (12), and other optical techniques (13) as well as computational theory (e.g., refs. 14-18 and references therein)]. These efforts, spanning almost 50 years, have led to a consensus view that ice VII moves gradually toward a symmetric H-bonded phase (ice X) across a broad pressure range with protons essentially localized between neighboring O-atoms on network sites. However, the positions of the hydrogen nuclei have not been determined directly at pressures sufficient to significantly change the molecular geometry from that found in common ice Ih (19). In addition, the nature of the proposed intermediate states between ices VII and X remains uncertain (11,20), and changes in ices VII and VIII themselves have been suggested by anomalies in X-ray (5,7,8,21,22) and spectroscopic (12,22,23) data beginning as low as 13-14 GPa.In contrast to other techniques, neutron diffraction can resolve the location of deuterons (D) directly within the l...

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supporting

confidence: 81%

“…The resulting powder data for samples 1-3 were fitted by Rietveldrefinement (26) using the conventional structure of ice VII (19,24,27) (Fig. 1A).…”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Neutron diffraction observations of interstitial protons in dense ice

Guthrie

Boehler

Tulk

et al. 2013

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

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“…In the ice VII structure each oxygen atom has eight nearest neighboring O atoms at a distance of about 2.90 Å; it forms a hydrogen bond with four of them, whereas the rest four neighboring O atoms belong to the other water framework, i.e., they are not hydrogen-bonded with the O atom under consideration [21,23]. Alternatively, in the ice VIII structure each O atom has two of four not bonded with it neighboring O atoms at a larger (3.32 Å) and two other at a smaller (2.74 Å) distance than the lengths of hydrogen bonds with yet another four O atoms (2.89 Å) [22,23].…”

Section: Results Of Simulation Of Crystalline Water Ices Ices Ih Icmentioning

confidence: 99%

Molecular dynamics study of crystalline water ices

Zheligovskaya

2008

J Struct Chem

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The behavior of structures of H 2 O crystalline ices Ih, Ic, XI, VII, VIII, VI is studied in molecular dynamics experiment using the potential offered by Poltev and Malenkov. The behavior of the system consisting of one of the two identical interpenetrating, but without any common hydrogen bonds, water frameworks comprising the ice VI structure is also simulated. As a result of simulations, the ice VII structure has collapsed, whereas other systems proved to be stable. The reasons of instability of the ice VII and previously studied ice IV structures in molecular dynamics experiments are discussed. Based on the simulation results of the above-mentioned ices and previous simulation of ices II, III, IX, IV, and XII, the general regularities of dynamic properties of water molecules in crystalline water ices are formulated. Unreliability of results obtained by molecular dynamics in the investigation of self-organizing processes in aqueous systems is shown.

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Einander durchdringende Netze: geordnete, periodische Verschlingung

1998

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Unauflöslich ineinander verwoben sind in vielen Festkörperstrukturen von polymeren, über H‐Brücken gebundenen Netzen und von Koordinationspolymeren die als voneinander unabhängig betrachteten ein‐, zwei‐ oder gar dreidimensionalen Netzstrukturen. Rechts ist z. B. die gegenseitige Durchdringung der Adamantaneinheiten zweier diamantartiger Netze gezeigt. Aus der detaillierten Beschreibung und Systematik der mehrfachen gegenseitigen Durchdringung von derartigen Netzen in Festkörperstrukturen lassen sich unter anderem weitreichende Folgerungen für das Kristall‐Engineering ableiten.

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Disordered structure of D2O ice VII from i n s i t u neutron powder diffraction

Cited by 72 publications

References 12 publications

Neutron diffraction observations of interstitial protons in dense ice

Neutron diffraction observations of interstitial protons in dense ice

Molecular dynamics study of crystalline water ices

Einander durchdringende Netze: geordnete, periodische Verschlingung

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