Superconductivity of metal doped-boron-nitrogen clathrates under ambient pressure

The ${\mathrm{LaH}}_{10}$ superconductor has attracted much attention due to its near-room-temperature superconducting transition temperature. However, ${\mathrm{LaH}}_{10}$ requires extremely high pressure, about 200 GPa, to maintain its stability, thereby limiting its potential for industrial applications. Here, we perform the high-throughput structure searches of ${\mathrm{LaH}}_{10}$-like boron-nitrogen clathrate superconductors at ambient pressure. The calculated results reveal that the stabilities of main-group and transition metal doped-boron-nitrogen clathrates are affected by both the valence electrons and atomic radius of the guest metals, and the boron-nitrogen cages tend to accommodate small-sized guest metals. The guest metals transfer charges to the boron-nitrogen caged frameworks, forming stronger anion-cation interactions, and the strong polar covalent bonds formed between B and N enhance the structural stabilities of these boron-nitrogen clathrates. Four stable $M{(\mathrm{BN})}_{5}$ ($M=$ Na, Al, In, Tl) superconductors with ${T}_{c}$ values of 8, 22, 15, and 15 K, respectively, are uncovered. Our findings indicate that the $p$ orbitals of $p$-region metals and the $p$ orbitals of B and N atoms exhibit the high-occupancy rate at the Fermi level, increasing the electronic density of the states at the Fermi surface, facilitating the electron-phonon coupling, and enhancing the superconductivity. The present results enrich the database of boron-nitrogen based superconductors and provide a promising avenue for design and synthesis high-temperature superconductors at ambient pressure.