Generic rules for achieving room-temperature superconductivity in ternary hydrides with clathrate structures
Liangliang Liu, Feng Peng, Peng Song, Xiaohan Liu, Liying Zhang, Xiaowei Huang, Chunyao Niu, Chengyan Liu, Weifeng Zhang, Yu Jia, Zhenyu Zhang
Abstract
The discovery of superconductors with higher superconducting transition temperatures (${T}_{\mathrm{c}}$'s) at ambient physical conditions is a perpetual drive in fundamental studies and for practical applications. Here we conceptualize two generic rules for achieving this goal surrounding metal hydride superconductors. Rule 1: the metal skeletons should be composed of elements with an effective valency of 3 for efficient electron donation to hydrogen. Rule 2: the fractional occupancy of the metal ions should be $\ensuremath{\sim}0.4$ for maximal chemical squeezing on hydrogen. Guided by these rules, and based on first-principles approaches, we predict a collection of new hydride superconductors, including the representative examples of ${\mathrm{CaHfH}}_{12}$, with ${T}_{\mathrm{c}}$ of $\ensuremath{\sim}360$ K at 300 GPa, and ${\mathrm{CaZrH}}_{12}$, with ${T}_{\mathrm{c}}$ of $\ensuremath{\sim}290$ K at 200 GPa. These findings are expected to be instrumental in predictive discoveries of new high-${T}_{\mathrm{c}}$ hydride superconductors at lower pressures.