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High pressure and high temperature equation of state of gamma and liquid iron

Chen, George Q. and Ahrens, Thomas J. (1997) High pressure and high temperature equation of state of gamma and liquid iron. In: High-pressure materials research : symposium held December 1-4, 1998, Boston, Massachusetts, U.S.A. Materials Research Society Symposium Proceedings. Vol.499. No.499. Materials Research Society , Warrendale, PA, pp. 41-61. ISBN 1-55899-404-1.

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Shock-wave experiments on pure iron preheated to 1573 K were conducted in the 17–73 GPa range. The shock-wave equation of state of γ-iron at an initial temperature of 1573 K can be fit with u_s = 4.102 (0.015) km/s + 1.610(0.014) u_p with ρ_o = 7.413±0.012 Mg/m^3 We obtain for γ-iron's bulk modulus and pressure derivative the values: 124.7±1.1 GPa and 5.44±0.06, respectively. We present new data for sound velocities in the γ- and liquid-phases. In the γ-phase, to a first approximation, the longitudinal sound velocity is linear with respect to density: V_p = −3.13 (0.72) + 1.119(0.084) p(units for V_p and p are km/s and Mg/m^3, respectively). Melting was observed in the highest pressure (about 70–73 GPa) experiments at a calculated shock temperature of 2775±160 K. This result is consistent with a previously calculated melting curve (for ε-iron) which is close to those measured by Boehler [1] and Saxena et al. [2]. The liquid iron sound velocity data yields a Grüneisen parameter value of 1.63±0.28 at 9.37±0.02 Mg/m^3 at 71.6 GPa. The quantity γ_ρ is 15.2±2.6 Mg/m^3, which agrees with the uncertainty bounds of Brown and McQueen [3] (13.3–19.6 Mg/m^3). Based on upward pressure and temperature extrapolation of the melting curve of γ-iron, the estimated inner core-outer core boundary temperature is 5500±400 K, the temperature at the core-mantle boundary on the outer core side is 3930±630 K.

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Additional Information:© 1998 Materials Research Society. Research supported by NSF. We thank E. Gelle, M.Long, and A. Devora for experimental assistance. Contribution #8495, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California.
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Caltech Division of Geological and Planetary Sciences8495
Series Name:Materials Research Society Symposium Proceedings
Issue or Number:499
Record Number:CaltechAUTHORS:20141029-092819848
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Official Citation:George Q. Chen and Thomas J. Ahrens (1997). High Pressure and High Temperature Equation-of-State of Gamma and Liquid Iron. MRS Proceedings, 499, 41 doi:10.1557/PROC-499-41.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50988
Deposited On:29 Oct 2014 19:29
Last Modified:10 Nov 2021 19:04

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