2025 Theses Doctoral

Advanced Simulation Techniques for Mineral Physics Under Extreme Conditions

Wan, Tianqi

Understanding the behavior of Earth's lower mantle minerals under extreme conditions is crucial for elucidating the dynamics and composition of Earth's interior and similar exoplanetary environments. The extreme pressures and temperatures of Earth’s deep interior are challenging to replicate experimentally, making insights from 𝘢𝘣 𝘪𝘯𝘪𝘵𝘪𝘰 methods essential. However, these simulations face substantial challenges such as complex phase relations, strong electron correlations, and computational demands.

To address these challenges, we employ advanced simulation techniques to investigate mineral behavior under such conditions. Specifically, we develop deep-learning potentials to analyze the elastic properties of key silicate perovskites in Earth's lower mantle, focusing on MgSiO₃ and CaSiO₃. Our study provides a comprehensive evaluation of the pressure and temperature dependence of elastic moduli in MgSiO₃ while uncovering ferroelastic behavior and shear modulus anomalies associated with the tetragonal↔cubic phase transition in CaSiO₃.

Furthermore, we expand our investigation to iron-bearing minerals, such as ferropericlase (Mg₁₋ₓFeₓ)O and Fe²⁺-bearing 𝐼4̄2d-type Mg₂SiO₄ (𝑝𝑝𝑝𝑣), which are critical to the composition of super-Earth mantles. By exploring the spin-state transitions of iron in these minerals under ultra-high pressures, we reveal their electronic structures and stabilities. This integrated approach connects the study of iron-bearing minerals and silicate perovskites, offering key insights into the behavior of these materials under extreme conditions and enhancing our understanding of Earth's interior and exoplanetary mantles.