Boron-doped scandium clusters B@Scn-1-/0/+ with n=2-13: uncovering the smallest endohedrally doped cages

A comprehensive study using density functional theory with the PBE functional and the Def2-TZVP basis set investigates the pure Scn+/0/- and doped Scn-1B+/0/- clusters with n = 1-13 in three charged states. B@Sc6+/0/- clusters emerge as the smallest doped cages identified so far, distinguished by their near-perfect octahedral geometry, with a B atom centrally enclosed in the Sc6+/0/- cages. Structural analysis reveals size-dependent trends, with a critical size at n = 6, marking a transition from exohedral to endohedral configuration, and a shift in the substitution-addition pattern of the B atom within the pure Sc host. Incorporation of a B atom induces electron redistribution, stabilizes high spin states and reduces energetic degeneracy. B-doping enhances the stability of the initial Scn+/0/- clusters, showing a consistent preference for cationic isomers. A molecular orbital (MO) analysis provides a detailed explanation for the observed energy degeneracy among various stable spin states by delving into their electronic configurations.