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A new structural relaxation pathway of low-density amorphous ice

Shephard, JJ; Klotz, S; Vickers, M; Salzmann, CG; (2016) A new structural relaxation pathway of low-density amorphous ice. Journal of Chemical Physics , 144 , Article 204502. 10.1063/1.4951013. Green open access

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Abstract

Low-density amorphous (LDA) ice is involved in critical cosmological processes and has gained prominence as one of the at least two distinct amorphous forms of ice. Despite these accolades, we still have an incomplete understanding of the structural diversity that is encompassed within the LDA state and the dynamic processes that take place upon heating LDA. Heating the high-pressure ice VIII phase at ambient pressure is a remarkable example of temperature-induced amorphisation yielding LDA. We investigate this process in detail using X-ray diffraction and Raman spectroscopy and show that the LDA obtained from ice VIII is structurally different from the more “traditional” states of LDA which are approached upon thermal annealing. This new structural relaxation pathway involves an increase of structural order on the intermediate range length scale. In contrast with other LDA materials the local structure is more ordered initially and becomes slightly more disordered upon annealing. We also show that the cascade of phase transitions upon heating ice VIII at ambient pressure includes the formation of ice IX which may be connected with the structural peculiarities of LDA from ice VIII. Overall, this study shows that LDA is a structurally more diverse material than previously appreciated.

Type: Article
Title: A new structural relaxation pathway of low-density amorphous ice
Open access status: An open access version is available from UCL Discovery
DOI: 10.1063/1.4951013
Publisher version: http://doi.org/10.1063/1.4951013
Language: English
Additional information: Copyright © 2016 AIP Publishing. All rights reserved.
Keywords: Atomic, Molecular & Chemical, Chemistry, Physics, Inelastic Neutron-scattering, Glass-transition Behavior, Pure Liquid Water, Stacking Disorder, Low-temperature, Raman-spectrum, O-h, Pressure, Phases, Amorphization
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/1493385
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