High-temperature superconductivity of ternary Ca4BxC23−x clathrates at moderate pressure

The synthesis of SrB3C3 and the research on its analogs demonstrate the high-temperature superconductivity of ternary metal-boron-carbon clathrates at ambient or moderate pressure. Here, we explore the stability and superconductivity of calcium-doped and boron-substituted type-VIII carbon clathrates Ca4BxC23−x (x=0−23) at 25–100 GPa. Based on the structural features and density functional theory (DFT) calculations, we screened 8 388 608 possible B-decorated structures and ultimately identified five thermodynamically metastable superconductors. Among them, Ca4B10C13 (space group I4¯3m) exhibited the highest Tc of ∼101−109 K, between 25 and 100 GPa. The high Tc of Ca4B10C13 originates from strong electron-phonon coupling caused by phonon softening and high density of states at the Fermi level. Our findings suggest that metal-doped and boron-substituted carbon clathrates are promising high-temperature superconductors at moderate pressure. locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon Physics Subject Headings (PhySH)Crystal structureDoping effectsElectron-phonon couplingSuperconductivityBoridesCarbidesFirst-principles calculations