Compression of Ice to 210 Gigapascals: Infrared Evidence for a Symmetric Hydrogen-Bonded Phase

  title={Compression of Ice to 210 Gigapascals: Infrared Evidence for a Symmetric Hydrogen-Bonded Phase},
  author={Alexander F. Goncharov and Viktor V. Struzhkin and Maddury Somayazulu and Russell J. Hemley and Ho-kwang Mao},
  pages={218 - 220}
Protonated and deuterated ices (H2O and D2O) compressed to a maximum pressure of 210 gigapascals at 85 to 300 kelvin exhibit a phase transition at 60 gigapascals in H2O ice (70 gigapascals in D2O ice) on the basis of their infrared reflectance spectra determined with synchrotron radiation. The transition is characterized by soft-mode behavior of the ν3 O-H or O-D stretch below the transition, followed by a hardening (positive pressure shift) above it. This behavior is interpreted as the… 

Bond strengthening in dense H2O and implications to planetary composition

H2O is an important constituent in planetary bodies, controlling habitability and, in geologically-active bodies, plate tectonics. At pressures within the interior of many planets, the H-bonds in H2O

Polymorphism of superionic ice

Water is abundant in natural environments but the form it resides in planetary interiors remains uncertain. We report combined synchrotron X-ray diffraction and optical spectroscopy measurements of

Neutron diffraction observations of interstitial protons in dense ice

The motif of distinct H2O 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

Effect of salt on the H-bond symmetrization in ice

This study reveals that the presence of salt hinders proton order and hydrogen bond symmetrization, and pushes ice VII to ice X transformation to higher and higher pressures as the concentration of salt is increased.

Structure and disorder in ice VII on the approach to hydrogen-bond symmetrization

We have collected neutron-diffraction data of sufficient quality for structural refinement from deuterated ice VII to over 60 GPa. At these pressures, we are approaching the onset of molecular

In situ observations of a high-pressure phase of H2O Ice

A previously unknown solid phase of H2O has been identified by its peculiar growth patterns, distinct pressure-temperature melting relations, and vibrational Raman spectra that are consistent with a disordered anisotropic structure with some similarities to ice VI.

Brillouin scattering of H2O ice to megabar pressures.

Throughout this pressure range, there is no evidence for anomalous changes in compressibility, and the sound velocities and elastic moduli do not exhibit measurable discontinuous shifts with pressure.

In situ high-pressure x-ray diffraction study of H2O ice VII.

Axial and radial polycrystalline x-ray diffraction measurements reveal a splitting of diffraction lines accompanied by changes in sample texture and elastic anisotropy, providing evidence for a transition in ice VII near 14 GPa involving changes in the character of the proton order/disorder.

Modulated phases and proton centring in ice observed by X-ray diffraction up to 170 GPa

Because of its open hydrogen-bonded structure, ice shows many structural changes between different crystalline forms under high pressure. Crystallographic studies of these transitions have been

Kinetic boundaries and phase transformations of ice i at high pressure.

These extensive investigations provide previously missing information on the phase diagram of water, especially on the kinetic paths that result in formation of phases which otherwise are not accessible; these results are keys for understanding the phase relations including the formation of metastable phases.



Effect of high pressure on the Raman spectra of ice VIII and evidence for ice X

Raman spectra of H2O and D2O ice VIII have been measured up to 50 GPa at 100 K. The changes in line positions and intensities of ice VIII and the appearance of a new band above 40 GPa point to the

Ice under pressure: Transition to symmetrical hydrogen bonds

We have examined at a rudimentary level the quantum-mechanical many-body problem for coupled proton motions along hydrogen bonds in compressed ices. Four cases are considered: ice IC, ices VI1 and

The uncoupled O-H stretch in ice VII. The infrared frequency and integrated intensity up to 189 kbar

The integrated absorptivity of the O–H stretching vibration of a dilute solution of HDO in D2O ice VII and the peak frequencies of the O–H stretching, bending, and rotational vibrations of HDO have

Raman Spectroscopy Investigation of Ice VII and Deuterated Ice VII to 40 GPa. Disorder in Ice VII

New results concerning room temperature Raman spectra of ice VII and deuterated ice VII in the diamond anvil cell, respectively, to 40 and 77 GPa, are reported. Two overlapping lattice translational

High-density structures and phase transition in an ionic model of H2O ice.

A self-consistent ionic model of water (protons and O 2- ions) has been used to explore the low-temperature, high-pressure properties of ice and a phase transition is predicted at about 330 GPa from the observed, low-pressure, symmetric hydrogen-bonded cuprite structure to a fully ordered antifluorite structure.

Synchrotron infrared spectroscopy to 0.15 eV of H2 and D2 at megabar pressures.

New synchrotron infrared absorption and reflectivity techniques have been developed to test predicted band overlap metallization in H 2 and D2 above 150 GPa at various temperatures, putting new bounds on the optical conductivity and possible band-gap closure at the 150-GPa transition.

Ab initio studies on high pressure phases of ice.

Molecular-dynamics simulations show that a mode-softening description of the transition is appropriate and is predicted at 49 GPa, in good agreement with experiment, when proton quantum fluctuations are treated within mean-field theory.

Pressure-Tuned Fermi Resonance in Ice VII

An anharmonic coupling constant, which is related to the potential energy surface on which hydrogen-bonded protons oscillate, was found to range around 50 wave numbers through the resonant pressure range.

Neutron diffraction study of the structure of deuterated ice VIII to 10 GPa.

The pressure dependence of the structure of deuterated ice VIII has been studied by time-of-flight neutron powder diffraction up to 10 GPa and it appears that the form of the O-H potential is constant with pressure.