We performed room-temperature sound velocity and density measurements on a polycrystalline alloy, Fe0.89Ni0.04Si0.07, in the hexagonal close-packed (hcp) phase up to 108 GPa. Over the investigated pressure range the aggregate compressional sound velocity is similar to 9% higher than in pure iron at the same density. The measured aggregate compressional (V-P) and shear (V-S) sound velocities, extrapolated to core densities and corrected for anharmonic temperature effects, are compared with seismic profiles. Our results provide constraints on the silicon abundance in the core, suggesting a model that simultaneously matches the primary seismic observables, density, P-wave and S-wave velocities, for an inner core containing 4 to 5 wt.% of Ni and 1 to 2 wt.% of Si. (C) 2010 Elsevier B.V. All rights reserved.
Antonangeli, Danièle Siebert, Julien Badro, James Farber, Daniel L. Fiquet, Guillaume Morard, Guillaume Ryerson, Frédérick J.