Recent computational studies have predicted that rare-earth superhydrides are promising high-temperature superconductors. Of these phases having very high hydrogen content ($\mathrm{X}{\mathrm{H}}_n,n>6$, where X is the rare-earth atom) a cubic phase of lanthanum hydride, recently synthesized at 170 GPa and identified as $\mathrm{La}{{\mathrm{H}}_{10}}_{\pm x}$, is in good agreement with theoretical predictions. The experiments found that the stability of the phase extended to lower pressure and a distorted form was found on decompression. Here we examine the nuclear quantum effects and anharmonic dynamics on $\mathrm{La}{\mathrm{H}}_{10}$, including the behavior of the hydrogen sublattice in comparison with the predicted atomic metallic hydrogen at higher pressure. We also examine the vibrational dynamics and electronic properties of a distorted lower pressure phase of $\mathrm{La}{\mathrm{H}}_{10}$ and find that superconducting $T_c$ decreases relative to cubic but remains relatively high (i.e., 229–245 K).

• Received 9 July 2018
• Revised 10 September 2018

DOI:https://doi.org/10.1103/PhysRevB.98.100102