THEORETICAL-STUDY OF CUBIC STRUCTURES BASED ON FULLERENE CARBON CLUSTERS - C28C AND (C-28)(2)

We study a hypothetical form of solid carbon C28C, with a unit cell wh ich is composed of the C-28 fullerene cluster and an additional single carbon atom arranged in the zinc-blende structure. Using ab initio ca lculations, we show that this form of solid carbon has lower energy th an hyperdiamond, the recently proposed form composed of C-28 units in the diamond structure. To understand the bonding character of these cl uster-based solids, we analyze the electronic structure of C28C and of hyperdiamond and compare them to the electronic states of crystalline cubic diamond.