A comparison of the Ca3(PO4)2 and CaSiO3 systems, with a new structure refinement of tuite synthesized at 15 GPa and 1300 °c

Richard M. Thompson, Xiande Xie, Shuangmeng Zhai, Robert T Downs, Hexiong Yang

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Tuite, the high-pressure γ-form of the Ca3(PO 4)2 system, has been synthesized from chlorapatite at 15 GPa and 1300 °C using a multi-anvil apparatus. Its crystal structure was determined with single-crystal X ray diffraction. It is isostructural with palmierite, with space group R3̄m and unit-cell parameters a = 5.2522(9) and c = 18.690(3) Å. The structure of tuite is characterized by three distinct polyhedra, PO4, Ca1O12, and Ca2O10, that are translationally interconnected in the sequence of PO 4-Ca2O10-Ca1O12-Ca2O10-PO4 along the c axis. Comparison of the CaSiO3 and Ca3(PO 4)2 polymorphic systems shows a striking resemblance in the evolution of atomic packing arrangements as the polymorphic density increases. In both cases, the Ca atoms are progressively incorporated into the (Ca+O) close-packed monolayers, consistent with the hypothesis that close packing is a consequence of volume decrease as density increases. Based on this observation, we predict a possible high-pressure post-tuite phase.

Original languageEnglish (US)
Pages (from-to)1585-1592
Number of pages8
JournalAmerican Mineralogist
Volume98
Issue number8-9
DOIs
StatePublished - Aug 2013

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chlorapatite
anvils
polyhedrons
crystal structure
Monolayers
Crystal structure
X-ray diffraction
Single crystals
crystal
X ray diffraction
Atoms
single crystals
cells
diffraction
atoms
x rays
comparison
beta-tricalcium phosphate
parameter

Keywords

  • Ca(PO)
  • CaSiO
  • Close-packing
  • Perovskite
  • Pseudowollastonite
  • Tuite
  • Whitlockite
  • Wollastonite

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

A comparison of the Ca3(PO4)2 and CaSiO3 systems, with a new structure refinement of tuite synthesized at 15 GPa and 1300 °c. / Thompson, Richard M.; Xie, Xiande; Zhai, Shuangmeng; Downs, Robert T; Yang, Hexiong.

In: American Mineralogist, Vol. 98, No. 8-9, 08.2013, p. 1585-1592.

Research output: Contribution to journalArticle

Thompson, Richard M. ; Xie, Xiande ; Zhai, Shuangmeng ; Downs, Robert T ; Yang, Hexiong. / A comparison of the Ca3(PO4)2 and CaSiO3 systems, with a new structure refinement of tuite synthesized at 15 GPa and 1300 °c. In: American Mineralogist. 2013 ; Vol. 98, No. 8-9. pp. 1585-1592.
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