The equation of state of forsterite to 17.2 GPa and effects of pressure media

Robert T Downs, Chang Sheng Zha, Thomas S. Duffy, Larry W. Finger

Research output: Contribution to journalArticle

91 Citations (Scopus)

Abstract

Pressure-volume X-ray diffraction data were collected at eight pressures to 17.2 GPa for synthetic single-crystal forsterite, Mg2SiO4. Birch-Murnaghan equation-of-state parameters were determined to be K0 = 125(2) GPa and K′0 = 4.0(4). To ensure hydrostatic conditions, we monitored the diffraction-peak shapes while the sample was in different pressure media: 4:1 methanol-ethanol, He, and Ar. The diffraction peaks for forsterite in 4:1 methanol-ethanol at 12.2 GPa were broadened to such an extent that we believe that any data collected at similar pressures and in this medium may be suspect and should be examined critically. The diffraction-peak profiles for the sample in He were sharp and well-formed, suggesting He provides an excellent medium at pressures ≤ 17.2 GPa. However, upon decompression, the diffraction peaks of the sample in He also showed significant broadening. This broadening suggests that with increasing pressure He diffused into the crystal, but with the release of pressure the He was unable to diffuse out quickly. The diffraction peaks regained their sharpness after several months.

Original languageEnglish (US)
Pages (from-to)51-55
Number of pages5
JournalAmerican Mineralogist
Volume81
Issue number1-2
StatePublished - Jan 1996
Externally publishedYes

Fingerprint

forsterite
Equations of state
equation of state
equations of state
diffraction
Diffraction
Methanol
methanol
ethanol
ethyl alcohol
Ethanol
methyl alcohol
crystal
sharpness
pressure reduction
decompression
hydrostatics
effect
X-ray diffraction
Single crystals

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

The equation of state of forsterite to 17.2 GPa and effects of pressure media. / Downs, Robert T; Zha, Chang Sheng; Duffy, Thomas S.; Finger, Larry W.

In: American Mineralogist, Vol. 81, No. 1-2, 01.1996, p. 51-55.

Research output: Contribution to journalArticle

Downs, RT, Zha, CS, Duffy, TS & Finger, LW 1996, 'The equation of state of forsterite to 17.2 GPa and effects of pressure media', American Mineralogist, vol. 81, no. 1-2, pp. 51-55.
Downs, Robert T ; Zha, Chang Sheng ; Duffy, Thomas S. ; Finger, Larry W. / The equation of state of forsterite to 17.2 GPa and effects of pressure media. In: American Mineralogist. 1996 ; Vol. 81, No. 1-2. pp. 51-55.
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