P‐V‐T equation of state for ε‐iron up to 80 GPa and 1900 K using the Kawai‐type high pressure apparatus equipped with sintered diamond anvils

Abstract

[1] In order to determine the P-V-T equation of state of ɛ-iron, in situ X-ray observations were carried out at pressures up to 80 GPa and temperatures up to 1900 K using the Kawai-type high pressure apparatus equipped with sintered diamond anvils which was interfaced with synchrotron radiation. The present results indicate the unit cell volume at ambient conditions V 0 = 22.15(5) Å 3 , the isothermal bulk modulus K T0 = 202(7) GPa and its pressure derivative K′ T0 = 4.5(2), the Debye temperature q 0 = 1173(62) K, Grüneisen parameter at ambient pressure g 0 = 3.2(2), and its logarithmic volume dependence q = 0.8(3). Furthermore, thermal expansion coefficient at ambient pressure was determined to be a 0 (K À1 ) = 3.7(2) Â 10 À5 + 7.2(6) Â 10 À8

Thermal equation of state of hcp‐iron: Constraint on the density deficit of Earth's solid inner core

“…Comparison of seismic observation with experimental data has shown that the density of the core is less than that of pure iron, known as the density deficit [Birch, 1952]. Compression of hcp-Fe has been extensively studied to multi-megabar pressures to better constrain the density of iron at core pressures [Mao et al, 1990;Dubrovinsky et al, 2000;Dewaele et al, 2006;Yamazaki et al, 2012;Sakai et al, 2014]. This value is then used to determine the contributions of Ni and light elements to the density of the core.…”

“…Dewaele et al [2006] determined the room temperature compression curve of iron under quasi-hydrostatic conditions using helium (He) (up to 197 GPa) and neon (Ne) (up to 205 GPa) as the pressure-transmitting media. More recently, Yamazaki et al [2012] obtained compression data of iron up to 80 GPa in the multianvil apparatus using gold (Au) as the pressure standard, and Sakai et al [2014] performed the compression experiment in the diamond anvil cell up to 280 GPa using NaCl as the pressure standard. More recently, Yamazaki et al [2012] obtained compression data of iron up to 80 GPa in the multianvil apparatus using gold (Au) as the pressure standard, and Sakai et al [2014] performed the compression experiment in the diamond anvil cell up to 280 GPa using NaCl as the pressure standard.…”

“…also shows the recent compression data ofYamazaki et al [2012] andSakai et al [2014] who performed the experiments in the multianvil press with sintered diamond anvils and the DAC, respectively. The multianvil data are limited to 80 GPa, and the pressures were calculated from the Au scale proposed byTsuchiya [2003].…”

Thermal equation of state and thermodynamic properties of iron carbide Fe3C to 31 GPa and 1473 K

“…However, more recent estimations for the core density deficit are still approximately the same as those proposed by Birch []. The density deficits vary from 5 to 12% for the outer core [ Stevenson , ; Anderson and Isaak , ] and from 3 to 5% for the inner core [ Stixrude et al ., ; Dubrovinsky et al ., ; Komabayashi and Fei , ; Yamazaki et al ., ]. In addition to the density deficit, the core has lower sound velocities with respect to pure iron, which also provides evidence for light element addition [ Fiquet et al ., ; Lin et al ., ].…”

Thermodynamics and Equations of State of Iron to 350 GPa and 6000 K

“…During the last several years, a significant amount of new P–V–T data for fcc-Fe and hcp-Fe, especially at very high temperatures, have appeared61325262728 and, in addition, the melting curve of Fe was shifted to higher temperatures according to measurements in ref. 14.…”