Compression of witherite to 8 GPa and the crystal structure of BaCO3II

C. M. Holl, J. R. Smyth, H. M.S. Laustsen, S. D. Jacobsen, R. T. Downs

Research output: Contribution to journalArticlepeer-review

56 Scopus citations

Abstract

Natural witherite (Ba0.99Sr0.01CO3) has been studied by single-crystal X-ray diffraction in the diamond anvil cell at eight pressures up to 8 GPa. At ambient pressure, cell dimensions are a = 5.3164(12) Å, b = 8.8921(19) Å, c = 6.4279(16) Å, and the structure was refined in space group Pmcn to R(F) = 0.020 from 2972 intensity data. The unit cell and atom position parameters for the orthorhombic cell were refined at pressures of 1.2, 2.0, 2.9, 3.9, 4.6, 5.5, 6.2, and 7.0 GPa. The volume-pressure data are used to calculate equation of state parameters K(T0) = 50.4(12) GPa and K' = 1.9(4). At approximately 7.2 GPa, a first-order transformation to space group P31c was observed. Cell dimensions of the high-pressure phase at 7.2 GPa are a = 5.258(6) Å, c = 5.64(1) Å. The high pressure structure was determined and refined to R(F) = 0.06 using 83 intensity data, of which 15 were unique. This high-pressure phase appears to be more compressible than the orthorhombic phase with an estimated initial bulk modulus (K(7.2GPa)) of 10 GPa.

Original languageEnglish (US)
Pages (from-to)467-473
Number of pages7
JournalPhysics and Chemistry of Minerals
Volume27
Issue number7
DOIs
StatePublished - Jan 1 2000

Keywords

  • Aragonite
  • Crystal structure
  • High pressure
  • Witherite

ASJC Scopus subject areas

  • Materials Science(all)
  • Geochemistry and Petrology

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