Physics
Scientific paper
Feb 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002pepi..129..301z&link_type=abstract
Physics of the Earth and Planetary Interiors, Volume 129, Issue 3-4, p. 301-311.
Physics
22
Scientific paper
Volume measurements for magnesiowüstite (Mg0.6Fe0.4)O, were carried out up to pressures of 10.1GPa in the temperature range 300-1273K, using energy-dispersive synchrotron X-ray diffraction. These data allow reliable determination of the temperature dependence of the bulk modulus and good constraint on the thermal expansitivity at ambient pressure which was previously not known for magnesiowüstite. From these data, thermal and elastic parameters were derived from various approaches based on the Birch-Murnaghan equation of state (EOS) and on the relevant thermodynamic relations. The results from three different equations of state are remarkably consistent. With (∂KT/∂P)T fixed at 4, we obtained K0=158(2)GPa, (∂KT/∂T)P=-0.029(3)GPaK-1, (∂KT/∂T)V=-3.9(+/-2.3)×10- 3GPaK-1, and αT=3.45(18)×10- 5+1.14(28)×10-8T. The K0, (∂KT/∂T)P, and (∂KT/∂T)V values are in agreement with those of and are similar to previously determined values for MgO. The zero pressure thermal expansitivity of (Mg0.6Fe0.4)O is found to be similar to that for MgO (). These results indicate that, for the compositional range /x=0-0.4 in (Mg1-xFex)O, the thermal and elastic properties of magnesiowüstite exhibit a dependence on the iron content that is negligibly small, within uncertainties of the experiments. They are consequently insensitive to the Fe-Mg partitioning between (Mg, Fe)SiO3 perovskite and magnesiowüstite when applied to compositional models of the lower mantle. With the assumption that (Mg0.6Fe0.4)O is a Debye-like solid, a modified equation of heat capacity at constant pressure is proposed and thermodynamic properties of geophysically importance are calculated and tabulated at high temperatures.
Kostak Paul
Zhang Jianzhong
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