Optimal alloying in hydrides: Reaching room-temperature superconductivity in LaH10

Doping represents one of the most promising avenues for optimizing superconductors, such as high-pressure conventional superconductors with record-breaking critical temperatures. In this work, we perform an extensive search for substitutional dopants in LaH10, looking for elements that enhance its electronic structure. In total, 70 elements were investigated as possible substitutions of La-sites at doping ratio of 12.5% under high pressure. To accelerate the screening of the ternary phases, our protocol to scan the chemical space is 1) to be constrained to highly symmetric patterns of hydrogen atoms, 2) focusing on phases with compact basis of lanthanum atoms (minimize enthalpy) and 3) to choose candidate dopants that preserve the van Hove singularity around the Fermi level. We found Ca as the best candidate dopants, which shift the van Hove singularity and increase the electronic DOS at the Fermi level. By using harmonic-level phonon calculations and performing first-principles calculation of Tc, Ca-doped LaH10 shows Tc which is 15% higher than the one of LaH10. It provides a promising route to reach room-temperature superconductivity in pressurized hydrides by doping.