Enhancement mechanism of electron–phonon coupling in <i>X</i>B₃ (<i>X</i> = K and Rb) compounds with Kagome lattice

Kagome superconductors are a recent hot topic in superconductivity, while most studies focus on ternary systems. This study investigated the Kagome lattice and other structure properties of binary <i>X</i>B₃ (<i>X</i> = K and Rb) compounds in the pressure range of 0-30 GPa using crystal structure prediction and first-principles calculations. The crystal properties and bonding characteristics of the <i>Cmmm</i>, <i>I</i>4/<i>mmm</i>, <i>P</i>6/<i>mmm</i>, and <i>P</i>6₃/<i>mmc</i> phases were analyzed. The electronic band and density of states revealed that the <i>I</i>4/<i>mmm</i> and <i>P</i>6₃/<i>mmc</i> phases exhibit a semiconducting behavior. In contrast, the <i>P</i>6/<i>mmm</i> phase displays a Kagome lattice, and metallic and low Vickers hardness behaviors. Furthermore, superconducting critical temperatures (<i>T</i>_c) of the <i>P</i>6/<i>mmm</i> phase have been calculated, with <i>T</i>_c values of 26.7 and 28.2 K for KB₃ and RbB₃ at 0 GPa, respectively. The enhancement mechanism of electron-phonon coupling is discussed in detail, thereby revealing the intrinsic connection between the Kagome lattice and superconductivity in <i>X</i>B₃_<i>P</i>6/<i>mmm</i> compounds. Our results indicate that the <i>X</i>B₃ compounds demonstrate outstanding properties, including semiconducting behavior and the Kagome lattice, providing valuable theoretical insights for the exploration of new semiconductors and superconductors.