P-V-T equation of state of lawsonite |
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| Authors: | I Daniel G Fiquet P Gillet M W Schmidt M Hanfland |
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| Institution: | (1) Laboratoire de Sciences de la Terre, UMR CNRS 8515, ENS Lyon and Université Claude Bernard Lyon I, Bat 402, 43 Bd du 11 Novembre, F-69622 Villeurbanne cedex, France e-mail: i-daniel@univ-lyon1.fr Fax: +33-4-72448593, FR;(2) UMR 6224, Université Blaise Pascal, 5 rue Kessler, F-63038 Clermont Ferrand cedex, France, FR;(3) European Sychrotron Radiation Facility, BP 220, F-38043 Grenoble cedex, France, FR |
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| Abstract: | A pressure-volume-temperature data set has been obtained for lawsonite CaAl2Si2O7(OH)2.H2O], using synchrotron X-ray diffraction and an externally heated diamond anvil cell. Unit-cell volumes were measured to 9.4
GPa and 767 K by angle dispersive X-ray diffraction using imaging plates. Phase changes were not observed within this pressure-temperature
range, and lawsonite compressed almost isotropically at constant temperature. The P-V-T data have been analyzed using a Birch-
Murnaghan equation of state and a linear equation of state expressed as β=–1/V0 (∂V/∂P)
T
. At room temperature, the derived equation of state parameters are: K
0=124.1 (18) GPa K'0 set to 4) and β–1=142.0(24) GPa, respectively. Our results are intermediate between previously reported measurements. The high-temperature
data show that the incompressibility of lawsonite decreases with increasing temperature to ∼500 K and then increases above.
Hence, the second order temperature derivative of the bulk modulus is taken into account in the equation of state; a fit of
the volume data yields K
0=123.9(18) GPa, (∂K/∂T)P=–0.111(3) GPa K–1, (∂2
K/∂T
2)P=0.28(6) 10–3 GPa K–2, α0=3.1(2) 10–5 K–1, assuming K'0=4.
Received: 2 June 1998 / Revised, accepted: 12 Ocotber 1998 |
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| Keywords: | Lawsonite Equation of state X-ray diffraction High-pressure High-temperature |
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