Electron-Phonon Coupling: II

δ-AlOOH is a key high-pressure hydrous mineral, known for its pressure-induced hydrogen bond symmetrization transition at 300 K. Raman and infrared measurements have revealed significant phonon anomalies in the 5–18 GPa range, including phonon softening near the transition pressure. However, traditional harmonic phonon calculations fail to capture these effects accurately due to the absence of anharmonic and other dynamic effects.

This study demonstrates that phonon quasiparticle properties derived from molecular dynamics simulations successfully replicate Raman and infrared observations, explaining the phonon anomalies. We observe broadened line widths and substantial frequency shifts, leading to phonon softening at lower pressures. This confirms the presence of pronounced anharmonicity and dynamic disorder throughout the H-bond symmetrization transition in δ-AlOOH. These findings underscore the critical role of anharmonic and other dynamic effects in understanding the behavior of hydrous minerals under extreme conditions of Earth’s interior.