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Updated: May 10, 2026
10:10
Neutron Crystallography Data Collection and Processing for Modelling Hydrogen Atoms in Protein Structures
Published on: December 1, 2020
Neutron diffraction observations of interstitial protons in dense ice.
Malcolm Guthrie1, Reinhard Boehler, Christopher A Tulk
1Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA. mguthrie@ciw.edu
Summary
High-pressure neutron diffraction reveals that ice under extreme conditions does not follow conventional models. Deuterons shift to interstitial sites, forming a new "interstitial" ice VII structure.
Area of Science:
- Condensed matter physics
- Materials science
- Geophysics
Background:
- The structure of hydrogen-bonded networks in ice is thought to persist even at high pressures.
- It is generally assumed that protons remain localized within these networks after molecular dissociation.
Purpose of the Study:
- To investigate the structural changes and deuteron locations in heavy water (D2O) at extreme pressures up to 52 GPa.
- To challenge the conventional understanding of hydrogen bonding and ice structures at high pressures.
Main Methods:
- Neutron diffraction measurements on D2O.
- High-pressure sample generation up to 52 GPa.
Main Results:
- A structural change was observed around 13 GPa.
- Above 26 GPa, the conventional ice VII network structure could not describe the data.
- Substantial deuteron density was found in the octahedral, interstitial voids of the oxygen lattice, indicating an "interstitial" ice VII form.
Conclusions:
- The conventional model of hydrogen bonding in ice is insufficient at high pressures.
- The newly observed "interstitial" ice VII structure provides a new framework for understanding ice evolution.
- This finding has implications for understanding dense matter and planetary interiors, potentially as a precursor to the superionic phase.
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