First-principles thermal equation of state and thermoelasticity of hcp Fe at high pressures

Abstract

We investigate the equation of state and elastic properties of hcp iron at high pressures and high temperatures using first principles linear response linear-muffin-tin-orbital method in the generalized-gradient approximation. We calculate the Helmholtz free energy as a function of volume, temperature, and volume-conserving strains, including the electronic excitation contributions from band structures and lattice vibrational contributions from quasi-harmonic lattice dynamics. We perform detailed investigations on the behavior of elastic moduli and equation of state properties as functions of temperature and pressure, including the pressure-volume equation of state, bulk modulus, the thermal expansion coefficient, the Gruneisen ratio, and the shock Hugoniot. Detailed comparison has been made with available experimental measurements and theoretical predictions.

33 pages, 12 figures

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• Iron Partitioning between Ferropericlase and Bridgmanite in the Earth's Lower Mantle
• Thermodynamic properties of ε-Fe with thermal electronic excitation effects on vibrational spectra
• Electrical Conductivity of Iron in Earth's Core from Microscopic Ohm's Law
• A Variable Polytrope Index Applied to Planet and Material Models
• The temperature-dependent elastic properties of B2-MgRE intermetallic compounds from first principles
• Impact of Electronic Correlations on High-Pressure Iron: Insights from Time-Dependent Density Functional Theory