LAUSR

Abstract We carried out sound velocity and density measurements on solid hcp-Fe and an hcp-Fe–Si alloy with 9 wt.% Si at 300 K up to ∼170 and ∼140 GPa, respectively. The results allow us to assess the density (ρ) dependence of the compressional sound velocity ( V P ) and of the shear sound velocity ( V S ) for pure Fe and the Fe–Si alloy. The established V P –ρ and V S –ρ relations are used to address the effect of Si on the velocities in the Fe–FeSi system in the range of Si concentrations 0 to 9 wt.% applicable to the Earth's core. Assuming an ideal linear mixing model, velocities vary with respect to those of pure Fe by ∼ + 80 m / s for V P and ∼ − 80 m / s for V S for each wt.% of Si at the inner core density of 13 000 kg/m3. The possible presence of Si in the inner core and the quantification of its amount strongly depend on anharmonic effects at high temperature and on actual core temperature.