Equation of State of Liquid Iron under Extreme Conditions

The density of liquid iron has been determined up to 116 GPa and 4350 K via static compression experiments following an innovative analysis of diffuse scattering from liquid. The longitudinal sound velocity was also obtained to 45 GPa and 2700 K based on inelastic x-ray scattering measurements. Combining these results with previous shock-wave data, we determine a thermal equation of state for liquid iron. It indicates that Earth's outer core exhibits 7.5%–7.6% density deficit, 3.7%–4.4% velocity excess, and an almost identical adiabatic bulk modulus, with respect to liquid iron.Received 6 August 2019Accepted 10 March 2020DOI:https://doi.org/10.1103/PhysRevLett.124.165701© 2020 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasPressure effectsPhysical SystemsLiquidsTechniquesPressure techniquesX-ray diffractionX-ray scatteringCondensed Matter, Materials & Applied Physics