Structural and bonding properties of bcc-basedB80solids

A density-functional-theory investigation of bcc ${\text{B}}_{80}$ and ${\text{K}}_6{\text{B}}_{80}$ is presented. The calculations show that ${\text{B}}_{80}$ cages pack closely on a bcc lattice, with bond formation between atoms on both nearest-neighbor and next-nearest-neighbor molecules. While the binding energy of 9.9 eV/molecule is only about half that calculated for fcc ${\text{B}}_{80}$, potassium intercalation of bcc ${\text{B}}_{80}$ adds an ionic component to the binding to further stabilize the lattice. Both ${\text{B}}_{80}$ and ${\text{K}}_6{\text{B}}_{80}$ are calculated to be metallic. The electronic structure is analyzed in terms of ionic and covalent effects, and the bonding is discussed in terms of a balance between two- and three-center bonding.