Ferroelastic hysteresis, shear modulus softening, and the tetragonal↔cubic transition in davemaoite.

Cubic CaSiO3-perovskite (davemaoite), the third most abundant mineral in Earth's lower mantle, remains a key uncertainty in deep-Earth models. Using machine learning interatomic potentials and molecular dynamics simulations, we present a direct evidence of pronounced ferroelastic hysteresis near its tetragonal↔cubic transition. By isolating the intrinsic elastic response from anelastic relaxation and nonhydrostatic stress, we establish a robust upper-bound benchmark for sound velocities and elasticity models while revealing pronounced shear modulus softening across the transition. The confirmed ferroelasticity suggests substantial strain memory, seismic wave scattering, and strong attenuation if the transition is activated in regions of deeply subducted mid-ocean ridge basalt (MORB) accumulation. While pure CaPv may not undergo this transition at relevant conditions, it could occur in Ca(Si,Ti)O3, contributing to the low shear velocity regions in the deep mantle and above the core-mantle boundary.