Figure 3

The elastic wave velocities of the δ-Fe13 samples computed using the natural abundance of Fe: (a), v_P, (b), v_S, (c) v_Φ. Elastic wave velocities of other end-membered hydrous phases: δ-AlOOH^20,21,26, δ-(Al_0.956Fe_0.044)OOH (δ-Fe4)²³, and ε-FeOOH with low spin state of Fe³⁺²⁶ are also shown. PREM is shown by gray lines³⁶. The values indicated by solid and open symbols were obtained from room temperature experiments and calculations at 0 K, respectively. Abrupt reductions of v_P and v_Φ for the δ-Fe13 samples at 32 GPa and 37.1 GPa are due to the spin transition of Fe³⁺²². The numerical values for the data of δ-Fe13 samples in this figure are available in Table S2.