Thermodynamic properties of ε-iron with T-dependent phonons

ORAL

Abstract

The quasi-harmonic approximation (QHA) is an extremely powerful method for computing thermodynamic properties of materials at high pressures (P) and temperatures (T). However, anharmonicity, electronic excitations in metals, or both, introduce an intrinsic T-dependence on the phonon frequencies. Here, we investigate the effect of electronic excitations on the phonon frequencies and the implication for the thermodynamics properties of ε-Fe at extreme P, T conditions. Phonon-phonon interactions are disregarded here. Because phonon frequencies are T-dependent, we first obtain the entropy using the phonon gas model formula, still valid in the context of phonon-quasiparticles, and then the vibrational free energy by integrating the entropy. We demonstrate that inclusion of the electronic thermal excitation effect on phonon dispersions makes a significant difference in the thermodynamic properties of ε-Fe at Earth’s inner core conditions and beyond.

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Presenters

  • Hongjin Wang

    Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA, Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA.

Authors

  • Hongjin Wang

    Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA, Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA.

  • Qi Zhang

    Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA, Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA.

  • Jingyi Zhuang

    Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA, Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA.

  • Renata Wentzcovitch

    Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory (LDEO), and Applied Physics and Applied Mathematics (APAM), Columbia University in the City o, Department of Applied Physics and Applied Mathematics, Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, Columbia University, Department of Applied Physics and Applied Mathematics, Columbia University, Applied Physics and Applied Mathematics and Department of Earth and Environmental Sciences, Lamont Doherty Earth Observatory, Columbia University, Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA, Department of Applied Physics and Applied Mathematics, Columbia University in the City of New York, 500 W. 120th St., Mudd 200, MC 4701 New York, NY 10027, USA., Department of Applied Physics and Applied Mathematics; Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, 10027, USA