Structures of high and low density amorphous ice by neutron diffraction
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Updated: Sep 30, 2026

An Externally-Heated Diamond Anvil Cell for Synthesis and Single-Crystal Elasticity Determination of Ice-VII at High Pressure-Temperature Conditions
Published on: June 18, 2020
J L Finney1, A Hallbrucker, I Kohl
1Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom. j.finney@ucl.ac.uk
Abstract:
Neutron diffraction with isotope substitution is used to determine the structures of high (HDA) and low (LDA) density amorphous ice. Both "phases" are fully hydrogen bonded, tetrahedral networks, with local order similarities between LDA and ice Ih, and HDA and liquid water. Moving from HDA, through liquid water and LDA to ice Ih, the second shell radial order increases at the expense of spatial order. This is linked to a fifth first neighbor "interstitial" that restricts the orientations of first shell waters. This "lynch pin" molecule which keeps the HDA structure intact has implications for the nature of the HDA-LDA transition that bear on the current metastable water debate.
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