Structures of High and Low Density Amorphous Ice by Neutron Diffraction

Finney, John; Hallbrucker, Andreas; Kohl, Ingrid; Soper, A. K.; Bowron, Daniel T.

doi:10.1103/physrevlett.88.225503

Cited by 317 publications

(418 citation statements)

References 25 publications

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“…The latter is consistent with the absence of broken bonds [30]. Yet HDA has SRO different from crystalline ice, and actually closer to the liquid, due to the presence of an additional non-bonded molecule, on average, at non-tetrahedral locations within the first coordination shell [30]. Arguably this is the reason for the similarity of the main edge of HDA ice and water, which both have molecular density higher than crystalline ice.…”

supporting

confidence: 62%

X-Ray Absorption Signatures of the Molecular Environment in Water and Ice

2010

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The x-ray absorption spectra of water and ice are calculated with a many-body approach for electron-hole excitations. The experimental features, including the small effects of temperature change in the liquid, are quantitatively reproduced from molecular configurations generated by abinitio molecular dynamics. The spectral difference between the solid and the liquid is due to two major short range order effects. One, due to breaking of hydrogen bonds, enhances the pre-edge intensity in the liquid. The other, due to a non-bonded molecular fraction in the first coordination shell, affects the main spectral edge in the conversion of ice to water. This effect may not involve hydrogen bond breaking as shown by experiment in high-density amorphous ice.PACS numbers: 36.20. Ng, 71.15.Pd, 32.10.Dk, 78.20.Ci The nature of the hydrogen bond (H-bond) network in water continues to be at the center of scientific debate [1]. A few years ago high-resolution x-ray absorption spectra (XAS) probed the local order of liquid and crystalline water phases, including the effect of temperature in the liquid [2]. These experiments stirred a storm of controversy because of their interpretation suggesting that a large fraction (>80%) of H-bonds are broken in the liquid [2]. This would imply an environment consisting primarily of chains and rings of H-bonds, in stark contrast with the conventional near-tetrahedral picture supported by diffraction [3] and other thermodynamic and spectroscopic data [4,5]. The broken H-bond fraction was estimated from the intensity of the pre-edge, which is prominent in the liquid and was believed to be absent in bulk ice. Subsequent x-ray Raman spectra, however, showed that the pre-edge feature is present, albeit with different intensity, not only in the liquid, but also in hexagonal (Ih), cubic (Ic), low-density amorphous (LDA) and highdensity amorphous (HDA) ice [6]. This experiment reported another interesting observation, namely that water and HDA ice have spectra with the main-edge more prominent than the post-edge, while the opposite behavior occurs in Ih, Ic, and LDA ice. This is puzzling given that both LDA and HDA ice are disordered structures with an insignificant fraction of broken H-bonds. Spectral calculations, based on electronic density-functional theory (DFT) and near-tetrahedral liquid models, correctly predicted the presence of three spectral features in ice and water and associated the enhancement of the pre-edge intensity to broken H-bonds [7,8,9,10]. However, the agreement with experiment was only semiquantitative and the calculations did not identify the cause of the significant changes in main-and post-edge spectra. These effects were generically attributed to disorder [8], but this does not explain why LDA and HDA ice show opposite behavior [6]. Finally, no attempt was made to discuss the effect of temperature in the liquid spectra, for which contrasting experimental data have been reported [2,11,12,13].In this paper we use liquid structures generated by ab-initio MD to compute x-ra...

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confidence: 62%

X-Ray Absorption Signatures of the Molecular Environment in Water and Ice

2010

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“…Various spectroscopic techniques have been applied to characterize amorphous ice, including FTIR spectroscopy [14,15], Raman spectroscopy [16,17], X-ray diffraction [18,19] and neutron diffraction [20,21]. As expected, the radial distribution function from diffraction experiments confirms the absence of the long range periodic structure in the amorphous ices [4,22].…”

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confidence: 60%

Two-Dimensional Infrared Spectroscopy of Isotope-Diluted Low Density Amorphous Ice

2013

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We present two-dimensional (2D) infrared (IR) spectra of isotope diluted ice in its low density amorphous form. Amorphous ice, which is structurally more similar to liquid water than to crystalline ice, provides higher resolution spectra of the hydrogen bond potentials because all motion is frozen. In the case of OD vibration of HOD in H2O, diagonal and off-diagonal (intermode) anharmonicity as well as the relaxation rate of the first excited state increase with hydrogen bond strength in a consistent way. For the OH vibration of HOD in D2O, additional more specific couplings need to be taken into account to explain the 2D IR response, that is, a Fermi resonance with the HOD bend vibration and couplings to phonon modes that lead to quantum beating. The lifetime of the fist excited state, 240 fs, is the shortest ever reported for any phase of isotope diluted water. We present 2D IR spectra of isotope diluted ice in its low density amorphous form. Amorphous ice, which is structurally more similar to liquid water than to crystalline ice, provides higher resolution spectra of the hydrogen bond potentials because all motion is frozen. In the case of OD vibration of HOD in H2O, diagonal and off-diagonal (inter-mode) anharmonicity as well as the relaxation rate of the first excited state increases with hydrogen bond strength in a consistent way. For the OH vibration of HOD in D2O, additional more specific couplings need to be taken into account to explain the 2D IR response, that is, a Fermi resonance with the HOD bend vibration and couplings to phonon modes that lead to quantum beating. The lifetime of the fist excited state, 240 fs, is the shortest ever reported for any phase of isotope diluted water.

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“…At this temperature, radial distribution functions (RDFs) g(r) of LDA and HDA from experiments are available. 74,75 Figure 3 shows the oxygen-oxygen (OO) g(r) at five selected points during the compression/decompression cycle at T = 80 K. All RDFs reach a constant value of 1 for approximately r > 1 nm, consistent with the fact that the system is amorphous, with no long-range order. The amorphous character of these states is further evident from the snapshots shown in Fig.…”

Section: B Structure Of Lda and Hdamentioning

confidence: 71%

Pressure-induced transformations in computer simulations of glassy water

Chiu

Starr

Giovambattista

2013

The Journal of Chemical Physics

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Glassy water occurs in at least two broad categories: low-density amorphous (LDA) and highdensity amorphous (HDA) solid water. We perform out-of-equilibrium molecular dynamics simulations to study the transformations of glassy water using the ST2 model. Specifically, we study the known (i) compression-induced LDA-to-HDA, (ii) decompression-induced HDA-to-LDA, and (iii) compression-induced hexagonal ice-to-HDA transformations. We study each transformation for a broad range of compression/decompression temperatures, enabling us to construct a "P-T phase diagram" for glassy water. The resulting phase diagram shows the same qualitative features reported from experiments. While many simulations have probed the liquid-state phase behavior, comparatively little work has examined the transitions of glassy water. We examine how the glass transformations relate to the (first-order) liquid-liquid phase transition previously reported for this model. Specifically, our results support the hypothesis that the liquid-liquid spinodal lines, between a lowdensity and high-density liquid, are extensions of the LDA-HDA transformation lines in the limit of slow compression. Extending decompression runs to negative pressures, we locate the sublimation lines for both LDA and hyperquenched glassy water (HGW), and find that HGW is relatively more stable to the vapor. Additionally, we observe spontaneous crystallization of HDA at high pressure to ice VII. Experiments have also seen crystallization of HDA, but to ice XII. Finally, we contrast the structure of LDA and HDA for the ST2 model with experiments. We find that while the radial distribution functions (RDFs) of LDA are similar to those observed in experiments, considerable differences exist between the HDA RDFs of ST2 water and experiment. The differences in HDA structure, as well as the formation of ice VII (a tetrahedral crystal), are a consequence of ST2 overemphasizing the tetrahedral character of water. © 2013 AIP Publishing LLC.

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Structures of High and Low Density Amorphous Ice by Neutron Diffraction

Cited by 317 publications

References 25 publications

X-Ray Absorption Signatures of the Molecular Environment in Water and Ice

X-Ray Absorption Signatures of the Molecular Environment in Water and Ice

Two-Dimensional Infrared Spectroscopy of Isotope-Diluted Low Density Amorphous Ice

Pressure-induced transformations in computer simulations of glassy water

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