Phonon Density of States of Iron up to 153 Gigapascals

• Published in: Science (American Association for the Advancement of Science) Vol. 292; no. 5518; pp. 914 - 916
• Main Authors: Mao, H. K., Xu, J., Struzhkin, V. V., Shu, J., Hemley, R. J., Sturhahn, W., Hu, M. Y., Alp, E. E., Vocadlo, L., Alfè, D., Price, G. D., Gillan, M. J., Schwoerer-Böhning, M., Häusermann, D., Eng, P., Shen, G., Giefers, H., Lübbers, R., Wortmann, G.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for the Advancement of Science 04.05.2001; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: Alloys; Applied sciences; Condensed matter: structure, mechanical and thermal properties; Density; Diffraction; Earth; Earth core; Electromagnetic scattering; Electromagnetic waves; Energy; Exact sciences and technology; Geomagnetic fields; Geomagnetism; Grade Point Average; High pressure; Inner cores; Iron; Iron (Metal); Kinetics; Lattice dynamics; Magnetic properties; Metals. Metallurgy; Motion; Nickel; Noise spectra; Observations; Optics; Phonon states and bands, normal modes, and phonon dispersion; Phonons; Phonons and vibrations in crystal lattices; Physics; Scattering; Scientific Concepts; Seismology; Solid state physics; Specific heat; Structure; Thermodynamics; Ultrasonics; Velocity; Vibration research; X-ray diffraction; X-rays; United States; United Kingdom; Germany; X-ray scattering; Pressure effects; Inelastic scattering; Shear modulus; Transition elements; Phonon density of states; Iron; Ab initio calculations; Experimental study; Bulk modulus; High pressure
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1057670

We report phonon densities of states (DOS) of iron measured by nuclear resonant inelastic x-ray scattering to 153 gigapascals and calculated from ab initio theory. Qualitatively, they are in agreement, but the theory predicts density at higher energies. From the DOS, we derive elastic and thermodynamic parameters of iron, including shear modulus, compressional and shear velocities, heat capacity, entropy, kinetic energy, zero-point energy, and Debye temperature. In comparison to the compressional and shear velocities from the preliminary reference Earth model (PREM) seismic model, our results suggest that Earth's inner core has a mean atomic number equal to or higher than pure iron, which is consistent with an iron-nickel alloy.