High-temperature superconducting ternary Li−R−H superhydrides at high pressures (R=Sc,Y,La

Compressed clathrate superhydrides have been the most promising candidates for room-temperature superconductors since the theory-oriented findings of ${\mathrm{CaH}}_{6}, {\mathrm{YH}}_{9}, {\mathrm{LaH}}_{10}$ et. al., where the hydrogen clathrate framework was believed to play a critical role in improving superconductivity. Recently, a ternary superhydride of ${\mathrm{Li}}_{2}{\mathrm{MgH}}_{16}$ was predicted to be a ``hot'' superconductor with a theoretical ${T}_{c}$ value up to 473 K at 250 GPa, although it exhibits the metastable feature under high pressure. With the aim of seeking thermodynamically stable ternary clathrate superhydrides, by exploring the high-pressure phase diagram of the $\mathrm{Li}\text{--}R\text{--}\mathrm{H} (R=\mathrm{Sc},\mathrm{Y},\phantom{\rule{0.28em}{0ex}}\text{and}\phantom{\rule{0.28em}{0ex}}\mathrm{La})$ systems at 300 GPa, we identified several thermodynamically ternary superhydrides with high-temperature superconductivity. Among these predicted stable structures, as a result of extensive simulations, clathrate structured ${\mathrm{Li}}_{2}{\mathrm{YH}}_{17}$ and ${\mathrm{Li}}_{2}{\mathrm{LaH}}_{17}$ are predicted to be high-temperature superconductors with a superconducting critical temperature (${T}_{c}$) up to 108 and 156 K, at 200 and 160 GPa, respectively. Interestingly, a superhydride, $Immm$--${\mathrm{Li}}_{2}{\mathrm{ScH}}_{20}$, with mixed molecular and atomic hydrogen, is predicted to possess a high ${T}_{c}$ of 242 K at 300 GPa. The present results may stimulate the future experiment for the investigation of structural, electronic, and superconducting properties of metal-doped rare-earth superhydrides, which thus help the further design and discovery of superconducting clathrate superhydrides.