Superconductivity in Novel Actinide Filled Boron Carbon Clathrates

Recently, a large number of theoretical and experimental studies have reported the emergence of a new sp³ clathrate XB₃C₃, where X represents different metal doping elements. The potential high-temperature superconducting materials have been discovered. New-typical cage material with both strong covalent and superconducting properties has important scientific research significance. In recent years, Ac discovered as the first element of the actinide series, AcH₁₀ has a superconducting transition temperature (T_c) of 251 K, making it a potential room temperature superconductor. Therefore, in this article, first principles density functional theory is used to explore the crystal structure, lattice dynamics, electronic properties, and superconducting properties of AcB₃C₃, AcB₂C₄, and AcB₄C₂ doped with Ac elements based on the cage structures of XB₃C₃, XB₂C₄, and XB₄C₂. Research has found that AcB₂C₄ is difficult to synthesize within the 0–200 GPa range, and AcB₃C₃ exhibits an indirect bandgap semiconductor with a bandgap width of approximately 1.154 eV at atmospheric pressure. Based on the mechanical stability criterion, it can be inferred that AcB₃C₃ and AcB₄C₂ are brittle materials with high hardness and stiffness that are elastically stable. At the same time, AcB₄C₂ exhibits superconducting properties at ambient pressure, with T_c reaching 1.565 K. It has been observed that as pressure increases, the T_c value exhibits a trend of initially decreasing and then increasing. The superconducting mechanism is mainly influenced by intermediate-frequencies phonons, which then shift to the combination of low-frequencies and intermediate-frequencies phonons. This study provides guidance for the experimental synthesis of cage type compound superconducting materials and provides new ideas for exploring superconducting materials with high superconducting transition temperature.