The baddeleyite-type high pressure phase of Ca(OH)2

M. Kunz, Kurt Leinenweber, J. B. Parise, T. C. Wu, W. A. Bassett, K. Brister, D. J. Weidner, M. T. Vaughan, Y. Wang

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37 Scopus citations


A phase transition from Ca(OH)2 I (portlandite) to Ca(OH)2 II at high pressure and temperature has been confirmed, using in situ x-ray diffraction in a multianvil high pressure device (DIA). The structure was determined at 9.5 GPa and room temperature from data collected after heating the sample at 300°C at 7.2 GPa in a diamond anvil cell. Both the Le Bail fit and preliminary Rietveld refinement suggest that the new phase, which reverts to Ca(OH)2 I during pressure release, has a structure related to that of baddeleyite (ZrO1); it is monoclinic (P21/c) with a = 4.887(2), b = 5.834(2), c = 5.587(2), β = 99.74(2)°. The coordination number of Ca increases from six to seven (5 + 2) across the transition. At 500°C, the phase boundary is bracketed at 5.7 ± 0.4 GPa by reversal experiments performed in the DIA.

Original languageEnglish (US)
Pages (from-to)311-319
Number of pages9
JournalHigh Pressure Research
Issue number4-5
StatePublished - 1996


  • Ca(OH)
  • High pressure
  • Phase transition
  • X-ray diffraction

ASJC Scopus subject areas

  • Condensed Matter Physics


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