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Title: Phase transitions and hydrogen bonding in deuterated calcium hydroxide: High-pressure and high-temperature neutron diffraction measurements

In situ neutron diffraction measurements combined with the pulsed neutron source at the Japan Proton Accelerator Research Complex (J-PARC) were conducted on high-pressure polymorphs of deuterated portlandite (Ca(OD){sub 2}) using a Paris–Edinburgh cell and a multi-anvil press. The atomic positions including hydrogen for the unquenchable high-pressure phase at room temperature (phase II′) were first clarified. The bent hydrogen bonds under high pressure were consistent with results from Raman spectroscopy. The structure of the high-pressure and high-temperature phase (Phase II) was concordant with that observed previously by another group for a recovered sample. The observations elucidate the phase transition mechanism among the polymorphs, which involves the sliding of CaO polyhedral layers, position modulations of Ca atoms, and recombination of Ca–O bonds accompanied by the reorientation of hydrogen to form more stable hydrogen bonds. - Graphical abstract: Crystal structures of high-pressure polymorphs of Ca(OD){sub 2}, (a) at room temperature (phase II′) and (b) at high temperature (phase II), were obtained from in situ neutron diffraction measurements. - Highlights: • We measured in situ neutron diffraction of high-pressure polymorphs of Ca(OD){sub 2}. • Hydrogen positions of the high-pressure phase are first determined. • The obtained hydrogen bonds reasonably explain Raman peaks of OHmore » stretching modes. • A phase transition mechanism among the polymorphs is proposed.« less
Authors:
 [1] ;  [2] ;  [2] ; ;  [3] ;  [4] ;  [5] ;  [2] ;  [6] ;  [7] ;  [1]
  1. Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577 (Japan)
  2. (Japan)
  3. Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo 113-0033, Tokyo (Japan)
  4. Division of Earth and Planetary Sciences, Graduate School of Sciences, Hokkaido University, N10W8 Kita-ku, Sapporo 060-0810 (Japan)
  5. Quantum Beam Science Directorate, Japan Atomic Energy Agency, 2-4 Shirane Shirakata, Tokai-mura, Ibaraki 319-1195 (Japan)
  6. J-PARC Center, Japan Atomic Energy Agency, 2-4 Shirane Shirakata, Tokai-mura, Ibaraki 319-1195 (Japan)
  7. Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha Kashiwa, Chiba 277-8581 (Japan)
Publication Date:
OSTI Identifier:
22443416
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 218; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CALCIUM HYDROXIDES; CALCIUM OXIDES; CRYSTAL STRUCTURE; HYDROGEN; NEUTRON DIFFRACTION; NEUTRON SOURCES; PEAKS; PHASE TRANSFORMATIONS; PRESSES; PULSES; RAMAN SPECTROSCOPY