Dynamics and superconductivity in compressed lanthanum superhydride

Recent computational studies have predicted that rare-earth superhydrides are promising high-temperature superconductors. Of these phases having very high hydrogen content (XHₙ,n>6, where X is the rare-earth atom) a cubic phase of lanthanum hydride, recently synthesized at 170 GPa and identified as LaH₁₀_±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 LaH₁₀, 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 LaH₁₀ and find that superconducting Tc decreases relative to cubic but remains relatively high (i.e., 229--245 K).