Thermal equation of state of Fe3S and implications for sulfur in Earth's core
Thermal equation of state of Fe3S and implications for sulfur in Earth's core
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DOI：
10.1029/2005jb004091
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发表时间：
2006-06-29
影响因子：
3.9
通讯作者：
Prakapenka, Vitali B.
中科院分区：
文献类型：
--
作者：
Seagle, Christopher T.;Campbell, Andrew J.;Prakapenka, Vitali B.
利用同步X射线衍射和激光加热金刚石砧池（DAC）同时研究了[1]铁（Fe）和共存的Fe3S。研究了Fe3S在80gpa压力和2500k温度下的热态方程（EOS）。将三阶Birch-Murnaghan EOS拟合到室温数据中，得到体积模量K-0 = 156(7) GPa（括号中的值为标准差），压力导数K-0'= 3.8(3)。室温数据也与hcp-Fe的EOS进行了校准，以进行比较，并有助于确定Fe3S的热压贡献。该拟合得到的体积模量K-0 = 113(9) GPa，压力导数K-0'= 5.2(6)。假设Fe3S对热压力的贡献为δ P-thermal = α K-T δ T，其中α K-T为常数。数据的最佳拟合结果为alpha K-T = 0.011(2) GPa K-1。在高压、高温实验中，铁和Fe3S共存，且铁和Fe3S的密度关系与温度无关，呈线性关系。将数据外推到核心-地幔边界（CMB），假设CMB温度为3500 K，熔化导致2%的体积变化，并对核心的镍含量进行小调整，表明14.7(11)wt %的硫足以解决外核的密度赤字。
[1] Iron ( Fe) and coexisting Fe3S were studied simultaneously using synchrotron X- ray diffraction and a laser-heated diamond anvil cell (DAC). The thermal equation of state (EOS) of Fe3S was investigated up to pressures of 80 GPa and temperatures of 2500 K. Fitting a third-order Birch-Murnaghan EOS to the room temperature data yielded bulk modulus K-0 = 156( 7) GPa ( values in parentheses are standard deviation) and pressure derivative K-0'= 3.8( 3) calibrated against NaCl in the B2 structure. The room temperature data were also calibrated against the EOS of hcp-Fe for comparison and aid in the determination of the thermal pressure contribution of Fe3S. This fit yielded bulk modulus K-0 = 113( 9) GPa and pressure derivative K-0'= 5.2( 6). The thermal pressure contribution of Fe3S was assumed to be of the form Delta P-thermal = alpha K-T Delta T, where alpha K-T is constant. The best fit to the data yielded alpha K-T = 0.011( 2) GPa K-1. Iron and Fe3S coexisted in the high-pressure, high-temperature experiments, and a density relationship between Fe and Fe3S was found to be linear and independent of temperature. Extrapolation of the data to the core-mantle boundary (CMB), using an assumed temperature of 3500 K at the CMB, a 2% volume change associated with melting, and applying a small adjustment to account for the nickel content of the core indicates that 14.7(11) wt % sulfur is adequate to resolve the density deficit of the outer core.