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

In order to determine the P-V-T equation of state of -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 V₀ = 22.15(5) ų, the isothermal bulk modulus K_T0 = 202(7) GPa and its pressure derivative K_T0 = 4.5(2), the Debye temperature θ₀ = 1173(62) K, Grneisen parameter at ambient pressure γ₀ = 3.2(2), and its logarithmic volume dependence q = 0.8(3). Furthermore, thermal expansion coefficient at ambient pressure was determined to be α₀(K^-1) = 3.7(2) × 10 ^-5 + 7.2(6) × 10^-8(T-300) and Anderson-Grneisen parameter δ_T = 6.2(3). Using these parameters, we have estimated the density of -iron at the inner core conditions to be ∼3% denser than the value inferred from seismological observation. This result indicates that certain amount of light elements should be contained in the inner core as well as in the outer core but in definitely smaller amount.