High-temperature superconductivity in boron-carbon clathrates XYB₆C₆

Inspired by the recent synthesized boron-carbon clathrate SrB­₃C₃ at 50 GPa with an estimated superconducting critical temperature (T_c) of 42 K, a number of the XYB₆C₆ systems are studied by substitution of Sr with other elements using first-principles density functional calculations. The dynamical stabilities, electronic structures and superconducting properties of these systems are analyzed at ambient conditions. Several XYB₆C₆ phases with a calculated T_c above 70 K are found. The phase stability is analyzed using the chemical pressure technique.