Prediction of p-block-based ternary superconductors XC2H8 at low pressure

Achieving room-temperature superconductivity under ambient conditions is one of the most important goals in solid-state physics and material science. Recent discoveries of high-T_c superconductivity in binary hydrides H₃S and LaH₁₀ at high pressures have focused the search for room-temperature superconductors on dense hydrides with conventional phonon-mediated pairing mechanisms. In this study, we predict a novel family of superconducting ternary hydrides under moderate compression, XC₂H₈ (X = Ga, In, Tl, Sn, Pb, Sb, Bi, Te, Po). Unlike H₃S and LaH₁₀, these new materials are stable at just around 20 GPa. Among the analyzed compounds, SbC₂H₈ exhibits the highest critical temperature of 73 K at a pressure of 100 GPa, which is attributed to its energetically favorable high-symmetry crystal structure (\(Fm{\bar{3}}m\)), high density of states at the Fermi level (1.27 states/eV) and strong electron–phonon coupling constant (1.02). We expect that our findings provide crucial insights into achieving high-temperature superconductivity at moderate pressures and accelerate the progress of experimental research.