2025/08/24 by Di Cataldo, Simone, Sanna, Antonio, Boeri, Lilia
#Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Superconductivity (cond-mat.supr-con)
paper · doi:10.48550/arxiv.2508.17422
We identify a new family of XB12, boron-rich compounds formed by interconnected B12 icosahedra and electropositive guest atoms (X). These structures emerged from first-principles crystal structure prediction at 50 GPa, as part of a pressure-quenching strategy to discover superconductors that could be synthesized under pressure and retained at ambient conditions. The resulting structures are thermodynamically competitive, dynamically stable at zero pressure, and - when X is a mono- or trivalent element - metallic and superconducting. Predicted critical temperatures reach up to 42 K for CsB12, rivaling MgB2, the highest-Tc ambient-pressure conventional superconductor. We interpret the XB12 phase as a superatomic crystal: the B12 units retain their molecular identity while forming extended crystalline networks. Their delocalized orbitals support doping without structural destabilization, while their covalent bonding promotes strong electron-phonon coupling. Unlike MgB2, where superconductivity is driven by a narrow subset of phonon modes, the XB12 compounds exhibit broad, mode- and momentum-distributed coupling through both intra- and inter-superatomic vibrations. Our results highlight the XB12 family as a promising platform for metastable superconductivity and demonstrate the potential of superatoms as functional building blocks in solid-state materials design.