Thermodynamic properties at the Earth's core conditions and the shock-reduced isotherm of iron: A first-principles study

First-principles thermodynamic calculations for metal iron (Fe) at ultrahigh pressures and temperatures are reported. The calculated results can be divided into three major parts: (i) the static 300 K equation of state and the dynamic shock-wave Hugoniot at pressures up to 1000 GPa; (ii) the shock-reduced data for the 300 K isotherm; and (iii) the thermodynamic properties under the Earth's core conditions. The calculations are parameter free in the sense that the cold part of the Helmholtz free energy is calculated using the full-potential linearized augmented-plane-wave method within the generalized gradient approximation. The thermal part due to the lattice ions is calculated using the recently developed classical mean-field potential approach, and the thermal part due to the thermal electrons is calculated using the one-dimensional numerical integration technique. The calculated results agree well with the available experimental data.