Effect of Spin Orbit Coupling on Superconductivity Models for LaH₁₀

Systematic evaluation of spin orbit coupling (SOC) on models for superconducting LaH10 at pressure is based on ab initio DFT calculations with optimised experimental cell dimensions. Non-relativistic and relativistic DFT treatments of LaH10 band structures using either a cubic or primitive lattice reveal the presence of a cosine-shaped band crossing the Fermi level. Asymmetry of cosine-shaped bands is indicative of the superconducting gap and enables close matches of calculated Tc with experimental values for 135 GPa < P < 220 GPa. Using SOC to calculate DOS, van Hove singularities occur at −0.122(3) eV for pressures between 90 GPa and 250 GPa. DFT calculation with SOC reduces the optimised cell dimension non-linearly and with higher effect as pressure increases. We relate the inflection of reciprocal space cosine-shaped curves to intersecting planes of (h0l), (hk0) and (0kl) planes in the real space Fm3m structure. Electron density distributions associated with asymmetry of the LaH10 irregular chamfered cube is attributed to variations in hydrogen bonding with pressure and abrupt changes to lattice vibrations between 135 GPa and 220 GPa. Collective behaviour of hydrogen lattice vibrations and asymmetric changes to crystal structure are consistent with the dome-like format for experimental Tc values with pressure.