Berlin 2024 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 21: Transport in Materials: Diffusion, Conduction of Charge or Heat I

MM 21.3: Talk

Tuesday, March 19, 2024, 10:45–11:00, C 264

Phonon anharmonicity at lower mantle conditons: Consequences on the thermal conductivity of MgO — •Saadi Chabane, Paola Giura, Lorenzo Paulatto, and Daniele Antonangeli — Institut de minéralogie, de physique des matériaux et de cosmochimie, Sorbonne université, Paris, France

Understanding the properties of Magnesium oxide's (MgO) properties is essential for planetary sciences and technology, especially as a fundamental component in Earth's lower mantle (LM). This discussion explores the complex field of anharmonic effects due to phonon scatterings in MgO, specifically addressing their behavior under extreme high-pressure and high-temperature LM conditions. The objective is to determine the influence of these anharmonicities on lattice thermal conductivity. Conducting ab-initio analyses for two distinct scenarios: one simulating elevated temperatures up to 1223K and another replicating LM conditions with T-P values ranging from 1900K-24GPa to 3000K-130GPa. Our study employs Infrared and inelastic x-ray scattering observations performed in our team for benchmarking. A comparison with simulations validates joint Density Functional Perturbation Theory (DFPT) and self-consistent harmonic approximation (SSCHA) computations for vibrational energies and phonon lifetimes, ensuring theoretical predictions align with experimental data. Additionally, a simplified model is utilized to explore the impact of mass disorder on thermal conductivity. Descending into the lower mantle, our findings unveil an unexpected change in anharmonic properties, attributed to the interplay of extreme pressure and temperature.

Keywords: Anharmonicity; thermal conductivity; Phonons; Extreme conditions; Ab-initio