Sound velocities in iron to 110 gigapascals.
The dispersion of longitudinal acoustic phonons was measured by inelastic x-ray scattering in the hexagonal closed-packed (hcp) structure of iron from 19 to 110 gigapascals. Phonon dispersion curves were recorded on polycrystalline iron compressed in a diamond anvil cell, revealing an increase of the longitudinal wave velocity (VP) from 7000 to 8800 meters per second. We show that hcp iron follows a Birch law for VP, which is used to extrapolate velocities to inner core conditions. Extrapolated longitudinal acoustic wave velocities compared with seismic data suggest an inner core that is 4 to 5% lighter than hcp iron.
Fiquet
G
G
Laboratoire de Minéralogie et Cristallographie, UMR CNRS 7590, Université Paris VI, 4 Place Jussieu, 75252 Paris cedex 06, France. fiquet@lmcp.jussieu.fr
Badro
J
J
Guyot
F
F
Requardt
H
H
Krisch
M
M