The structural phase transition and physical properties of (Mg, Fe)SiO3 under high pressure

The underlying physical mechanisms of electrical conductivities and seismic properties of (Mg, Fe)SiO3 are crucial to understand the formation, evolution and dynamics of the Earth's mantle. Here, we have studied the phase stabilities, electrical conductivities and seismic properties of (Mg, Fe)SiO3 by first-principles calculations. Our calculations reveal that the post-perovskite (pPv) phases of (Mg, Fe)SiO3 exhibit enhanced stabilities under relatively low pressures with the increase of the iron contents. The electrical conductivities of (Mg, Fe)SiO3 are found to exhibit the sharp upward trend with increasing iron contents and temperatures. Most importantly, the influence of iron contents on electrical conductivities surpasses those of temperatures. The seismic wave velocities indicate that the presence of iron induces lower sound velocities and the weakening of anisotropies. At 136 GPa, the (Mg, Fe)SiO3 possesses the lowest Vs and Vp of 6.6 and 11.9 km/s, respectively. The minimum sound velocity anisotropy is 15.6%. These findings offer important insights for understanding the physical origins and mechanisms of the high conductivity layer and ultra-low sound velocity zones in Earth's interior, which are anticipated to exert a profound impact on the exploration of the complex geophysical processes occurring in the Earth.