Geometric, electronic, and optical properties of a boron-doped aluminum cluster of B ₂ Al₂₁^-: A density functional theory study

We present the physicochemical properties for the lowest-energy isomer of a boron-doped aluminum cluster of B₂Al21-. The isomer was obtained by basin-hopping minimization based on the density functional theory, starting from a face-sharing bi-icosahedral structure in which two boron atoms were endohedrally doped to each icosahedron. The lowest-energy isomer is a triangular form in which an aluminum cage encapsulates two boron atoms endohedrally. The electronic structure was analyzed by projecting Kohn-Sham orbitals onto the spherical harmonics; occupied and unoccupied frontier orbitals are dominantly G- and H-symmetries, respectively. Optical absorption is mainly assigned to G to H transitions.