Deep-learning-based prediction of the tetragonal$\to$cubic transition in davemaoite

Abstract

Davemaoite, i.e., $CaSi{O}_3$ perovskite (CaPv), is the third most abundant phase in the lower mantle and exhibits a tetragonal-cubic phase transition at high pressures and temperatures. The phase boundary in CaPv has recently been proposed to be close to the cold slab adiabatic and cause mid-mantle seismic wave speed anomalies (Thomson et al., Nature 572, 643, 2019). In this study, we utilized accurate deep-learning-based simulations and thermodynamic integration techniques to compute free energies at temperatures ranging from 300 to 3,000 K and pressures up to 130 GPa. Our results indicate that CaPv exhibits a single cubic phase throughout lower-mantle conditions. This suggests that the phase diagram proposed by Thomson et al. requires revision, and mid-mantle seismic anomalies are likely attributable to other mechanisms.

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Cited by in corpus (3)

• Melting Temperature of Iron Under the Earth's Inner Core Condition from Deep Machine Learning
• The Fe-Ni phase diagram and the Earth's inner core structure
• The thermodynamics of CaSiO3 in Earth's lower mantle