C28 fullerites - structure, electronic properties and intercalates

Mechanical and electronic properties of hypothetical carbon nanostructures, on the basis of C28 building blocks, hyperdiamond and hyperlonsdaleite, have been investigated by DFT-based methods. The low mass density and large internal surface suggest applications as catalyst, nanosieve and ga storage material. We estimate the active volume accessible by H2. Special emphasis is given to tune the properties by endo- and exohedral intercalation with Zn, Ti, and K. While endohedral intercalation with Zn does not affect the overall structure, endohedral Ti intercalation has different consequences on the structural stability of the two allotropes. Exohedral intercalation with K leads to an ionic fullerite phase with metallic conductivity.