Regensburg 2025 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 7: Materials for the Storage and Conversion of Energy
MM 7.5: Vortrag
Montag, 17. März 2025, 16:45–17:00, H22
Investigating phase diagram and phonons in superconducting Lanthanum Hydride through an accurate treatment of anharmonicity and nuclear quantum effects — •Abhishek Raghav1, Kousuke Nakano2, and Michele Casula1 — 1Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Sorbonne Université, Paris, France — 2Center for Basic Research on Materials, National Institute for Materials Science (NIMS), Tsukuba, Japan
Hydrogen rich materials with clathrate structures are an important class of superconducting materials. Lanthanum hydride (LaH10) is one such material, demonstrated to show superconductivity at 250 K and 170 GPa. Phase diagram, phonon spectrum and electron-phonon coupling are important ingredients used to predict superconductivity, being of BCS type. However, computing these accurately for hydrogen clathrate materials requires including anharmonicity due to nuclear quantum effects (NQE). In this work, we use the path integral molecular dynamics (PIMD) and the stochastic self-consistent harmonic approximation (SSCHA) to study NQE and finite temperature on the phase stability and phonons. In order to speed up PIMD and SSCHA calculations, we employ a machine learning potential generated using MACE. This allows us to explore the theoretical LaH10 phase diagram over an unprecedentedly wide range of temperatures and pressures. We found that, when quantum effects are included, hydrogen cage symmetrization occurs at lower pressures than in classical simulations, placing the maximum of Tc measured in experiments close to the quantum transition region.
Keywords: Lanthanum hydride; Superconductivity; Phonons; Molecular dynamics; Machine learning