Thermoelastic equation of state of jadeite NaAlSi{sub 2}O{sub 6}: An energy-dispersive Reitveld refinement study of low symmetry and multiple phases diffraction

Journal Article · Wed Jan 01 04:00:00 EST 1997 · Geophysical Research Letters

DOI:https://doi.org/10.1029/96GL03769· OSTI ID:534439

Zhao, Y; Von Dreele, R B; Shankland, T J ^[1]; Weidner, D J; Zhang, J; Wang, Y; Gasparik, T ^[2]

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1. Los Alamos National Laboratory, Los Alamos, New Mexico (United States)
2. State University of New York at Stony Brook, Stony Brook, New York (United States)

We report the first measurement of a complete set of thermoelastic equation of state of a clinopyroxene mineral. We have conducted an {ital in situ} synchrotron x-ray diffraction study of jadeite at simultaneous high pressures and high temperatures. A modified Rietveld profile refinement program has been applied to refine the diffraction spectra of low symmetry and multiple phases observed in energy dispersive mode. Unit cell volumes, measured up to 8.2 GPa and 1280 K, are fitted to a modified high-temperature Birch-Murnaghan equation of state. The derived thermoelastic parameters of the jadeite are: bulk modulus K{prime}=125 GPa with assumed pressure derivative of bulk modulus {dot K}={partial_derivative}K/{partial_derivative}P=5.0, temperature derivative of bulk modulus K={partial_derivative}K/{partial_derivative}T={minus}1.65{times}10{sup {minus}2}GPaK{sup {minus}1}, and volumetric thermal expansivity {alpha}=a+bT with values of a=2.56{times}10{sup {minus}5}K{sup {minus}1} and b=0.26{times}10{sup {minus}8}K{sup {minus}2}. We also derived thermal Gr{umlt u}neisen parameter {gamma}{sub th}=1.06 for ambient conditions; Anderson-Gr{umlt u}neisen parameter {delta}{sub To}=5.02, and pressure derivative of thermal expansion {tilde o}{alpha}/{tilde o}P={minus}1.06{times}10{sup {minus}6}K{sup {minus}1}GPa{sup {minus}1}. From the P{minus}V{minus}T data and the thermoelastic equation of state, thermal expansions at five constant pressures of 1.0, 2.5, 4.0, 5.5, and 7.5 GPa are calculated. The derived pressure dependence of thermal expansion is: {Delta}{alpha}/{Delta}P={minus}0.97{times}10{sup {minus}6}K{sup {minus}1}GPa{sup {minus}1}, in good agreement with the thermodynamic relations.{copyright} 1997 American Geophysical Union

• OSTI ID: 534439
• Journal Information: Geophysical Research Letters, Journal Name: Geophysical Research Letters Journal Issue: 1 Vol. 24; ISSN GPRLAJ; ISSN 0094-8276
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ALUMINIUM SILICATES
EQUATIONS OF STATE
GEOCHEMISTRY
SILICATE MINERALS
SODIUM SILICATES
THERMAL EXPANSION
THERMOELASTICITY
X-RAY DIFFRACTION