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Pressure-induced dissociation of water molecules in ice VII

The neutron diffraction pattern of D(2)O ice was recently measured at pressures up to 52 GPa by Guthrie et al., who proposed an octahedral interstitial model for ice at pressures above 13 GPa to account for the deviation of the observed crystal structure from that of ice VII. In this article, the oc...

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Autores principales: Iitaka, Toshiaki, Fukui, Hiroshi, Li, Zhi, Hiraoka, Nozomu, Irifune, Tetsuo
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Publishing Group 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4515761/
https://www.ncbi.nlm.nih.gov/pubmed/26212425
http://dx.doi.org/10.1038/srep12551
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author Iitaka, Toshiaki
Fukui, Hiroshi
Li, Zhi
Hiraoka, Nozomu
Irifune, Tetsuo
author_facet Iitaka, Toshiaki
Fukui, Hiroshi
Li, Zhi
Hiraoka, Nozomu
Irifune, Tetsuo
author_sort Iitaka, Toshiaki
collection PubMed
description The neutron diffraction pattern of D(2)O ice was recently measured at pressures up to 52 GPa by Guthrie et al., who proposed an octahedral interstitial model for ice at pressures above 13 GPa to account for the deviation of the observed crystal structure from that of ice VII. In this article, the octahedral interstitial model was re-examined in terms of the interstitial occupancy and X-ray Raman spectroscopy (XRS) spectra. The interstitial occupancy calculated using first-principles molecular dynamics simulations was negligibly small compared to that of the interstitial model. The oxygen K-edge spectra calculated for the interstitial model exhibited two additional low-energy peaks originating from water molecules and hydroxides that are interacting with interstitial protons, respectively, whereas these low-energy peaks were not observed in the experimentally measured spectra. These results suggest that the interstitial model cannot explain the XRS spectra of ice VII at pressures above 13 GPa and that more precise structure measurements and analyses are necessary to reveal the nature of the pressure-induced transition.
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spelling pubmed-45157612015-07-29 Pressure-induced dissociation of water molecules in ice VII Iitaka, Toshiaki Fukui, Hiroshi Li, Zhi Hiraoka, Nozomu Irifune, Tetsuo Sci Rep Article The neutron diffraction pattern of D(2)O ice was recently measured at pressures up to 52 GPa by Guthrie et al., who proposed an octahedral interstitial model for ice at pressures above 13 GPa to account for the deviation of the observed crystal structure from that of ice VII. In this article, the octahedral interstitial model was re-examined in terms of the interstitial occupancy and X-ray Raman spectroscopy (XRS) spectra. The interstitial occupancy calculated using first-principles molecular dynamics simulations was negligibly small compared to that of the interstitial model. The oxygen K-edge spectra calculated for the interstitial model exhibited two additional low-energy peaks originating from water molecules and hydroxides that are interacting with interstitial protons, respectively, whereas these low-energy peaks were not observed in the experimentally measured spectra. These results suggest that the interstitial model cannot explain the XRS spectra of ice VII at pressures above 13 GPa and that more precise structure measurements and analyses are necessary to reveal the nature of the pressure-induced transition. Nature Publishing Group 2015-07-27 /pmc/articles/PMC4515761/ /pubmed/26212425 http://dx.doi.org/10.1038/srep12551 Text en Copyright © 2015, Macmillan Publishers Limited http://creativecommons.org/licenses/by/4.0/ This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
spellingShingle Article
Iitaka, Toshiaki
Fukui, Hiroshi
Li, Zhi
Hiraoka, Nozomu
Irifune, Tetsuo
Pressure-induced dissociation of water molecules in ice VII
title Pressure-induced dissociation of water molecules in ice VII
title_full Pressure-induced dissociation of water molecules in ice VII
title_fullStr Pressure-induced dissociation of water molecules in ice VII
title_full_unstemmed Pressure-induced dissociation of water molecules in ice VII
title_short Pressure-induced dissociation of water molecules in ice VII
title_sort pressure-induced dissociation of water molecules in ice vii
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4515761/
https://www.ncbi.nlm.nih.gov/pubmed/26212425
http://dx.doi.org/10.1038/srep12551
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