Equations of State and Phase Transformations in Rocky Materials to TPa Pressures*

Recent advances in theory and technology have enabled constraining the equation of state (EOS) and phase transformation of materials to TPa pressures—conditions relevant to early Earth and large planets. This presentation summarizes our latest findings for a series of planetary materials listed below based on first-principles simulations and compared to laser-driven experiments when available:

(1) MgSiO₃. Hugoniots of enstatite and bridgmanite calculated to 1.4 TPa, in addition to the Grüneisen parameter as a function of temperature and density.¹

(2) SiO₂. Mechanism of the bonded-to-atomic transition in liquid silica clarified and a new transition boundary rendered based on calculations and extensive analysis of thermodynamic, structural, and electronic properties.²

(3) MgO. The B1–B2 phase boundary benchmarked by quantum Monte Carlo calculations and accurate free-energy data (via thermodynamic integration) at T = 0 K up to the triple point.³

(4) Al₂O₃. Melting curves of the post-perovskite and U₂S₃ phases constrained to 1 TPa.⁴

The results necessitate reconsideration of predictions by planetary models that are based on empirical EOS models.