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Thermodynamics of hexagonal-close-packed iron under Earth’s core conditions

Alfe, D.; Price, G.D.; Gillan, M.J.; (2001) Thermodynamics of hexagonal-close-packed iron under Earth’s core conditions. Physical Review B , 64 (4) 045123. 10.1103/PhysRevB.64.045123. Green open access

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Abstract

The free energy and other thermodynamic properties of hexagonal-close-packed iron are calculated by direct ab initio methods over a wide range of pressures and temperatures relevant to the Earth’s core. The ab initio calculations are based on density-functional theory in the generalized-gradient approximation, and are performed using the projector augmented wave approach. Thermal excitation of electrons is fully included. The Helmholtz free energy consists of three parts, associated with the rigid perfect lattice, harmonic lattice vibrations, and anharmonic contributions, and the technical problems of calculating these parts to high precision are investigated. The harmonic part is obtained by computing the phonon frequencies over the entire Brillouin zone, and by summation of the free-energy contributions associated with the phonon modes. The anharmonic part is computed by the technique of thermodynamic integration using carefully designed reference systems. Detailed results are presented for the pressure, specific heat, bulk modulus, expansion coefficient and Grüneisen parameter, and comparisons are made with values obtained from diamond-anvil-cell and shock experiments.

Type: Article
Title: Thermodynamics of hexagonal-close-packed iron under Earth’s core conditions
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevB.64.045123
Publisher version: http://dx.doi.org/10.1103/PhysRevB.64.045123
Language: English
Additional information: Phys. Rev. B 64, 045123 (2001) [16 pages]
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/8859
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