Prediction of high-temperature ambient-pressure superconductivity in hexagonal boron-rich clathrates

Inspired by recent predictions of superconductivity in B-C framework clathrates, we employ density functional theory to explore potential superconductors among hexagonal hydride-substituted compounds with compositions $X{\mathrm{B}}_{8}\mathrm{C}, X{\mathrm{B}}_{7}{\mathrm{C}}_{2}, X{\mathrm{B}}_{6}{\mathrm{C}}_{3}, X{\mathrm{B}}_{3}{\mathrm{C}}_{6}, X{\mathrm{B}}_{2}{\mathrm{C}}_{7}$, and $X{\mathrm{BC}}_{8}$. Our high-throughput calculations on 96 compounds reveal several dynamically stable candidates exhibiting superconductivity at ambient pressure. An analysis of the electronic structures and electron-phonon coupling demonstrates that ${\mathrm{CaB}}_{8}\mathrm{C}, {\mathrm{SrB}}_{8}\mathrm{C}$, and ${\mathrm{BaB}}_{8}\mathrm{C}$ possess superconducting transition temperatures (${T}_{c}$) exceeding 50 K, with ${\mathrm{CaB}}_{8}\mathrm{C}$ exhibiting the highest predicted ${T}_{c}$ of 77.1 K among all stable compounds studied. These findings expand the family of B-C clathrate superconductors and provide valuable insights for experimental efforts aimed at discovering different superconducting materials.