Superconductivity of LaH10 and LaH16 polyhydrides

Recent experiments have established previously predicted LaH10 as the highest-temperature superconductor, with TC up to 250–260 K [Drozdov et al., Nature (London) 569, 528 (2019); Somayazulu et al., Phys. Rev. Lett. 122, 027001 (2019)]. In this work we explore the high-pressure phase stability and superconductivity of lanthanum hydrides LaHm. We predict the stability of the hitherto unreported polyhydride P6/mmm−LaH16 at pressures above 150 GPa; at 200 GPa, its predicted superconducting TC is 156 K, the critical field μ0HC(0) is approximately 35 T, and the superconducting gap is up to 35 meV. We revisit the superconductivity of LaH10 and find its TC to be up to 259 K at 170 GPa from solving the Eliashberg equation and 271 K from solving the gap equation within the superconducting density functional theory, which also allows us to compute the Coulomb pseudopotential μ* for LaH10 and LaH16.