Machine learning assisted molecular dynamics study of the superhydride LaH₁₀

The study of metallic, Hydrogen-rich compounds in recent years has revived efforts toward room temperature superconductivity. One of these compounds is a Lanthanum superhydride, successfully synthesized and shown to superconduct up to 260 K [1,2]. First-principles electron-phonon calculations show that fcc-LaH₁₀ and slight rhombohedral distortions thereof are consistent with high temperature superconductivity. However, these calculations do not fully account for the dynamics of the Hydrogen sublattice, which is highly anharmonic. Using a machine learned interatomic potential, we characterize diffusion and distortion in LaH₁₀ with molecular dynamics. With access to larger length and time scales, we highlight the importance of finite-size effects and quantum effects. We find that proton diffusion begins at a lower temperature than previously expected. We also see how a rhombohedral distortion can appear as pressure is lowered, which experiments have observed.

[1] Somayazulu, Maddury et al. "Evidence for Superconductivity above 260 K in Lanthanum Superhydride at Megabar Pressures". Phys. Rev. Lett. 122. (2019): 027001.

[2] Drozdov, A. P. et al. "Superconductivity at 250 K in lanthanum hydride under high pressures". Nature 569. 7757(2019): 528-531.