9:15 AM - 9:30 AM
[SIT22-14] Implication of the B1-B2 phase transition on MgO diffusion properties in super-Earth mantles
Keywords:super-Earths, B2-type MgO, diffusion properties
To test the above hypothesis, we investigated self-diffusion in B2-type MgO via the vacancy mechanism by using first-principles calculations (Ritterbex et al. 2017). We elucidate that non-interacting vacancy pairs are most abundant in both the intrinsic and extrinsic regimes which may govern ionic diffusion. Across the phase transition, we find substantial reductions in defect energetics and show that the reduction in ionic migration enthalpy accounts for an increase in the effective MgO diffusion coefficient of ~104 at 500 GPa. Our examination of atomic relaxations demonstrates that diffusion controlled viscosity may generally decrease across high-pressure phase transitions with increasing coordination number. Our results suggest mantle convection in the deep interior of super-Earths to be more vigorous than previously thought.