First-principles investigation of structural and electronic properties of solid cubane and its doped derivatives

The electronic and structural properties of molecular and solid cubane have been studied by first-principles, self-consistent field total energy calcu lations. Calculated molecular properties such as equilibrium geometry and e lectronic and vibrational spectra are found to be in good agreement with ex perimental data. Structural parameters and the energetics of both the low-t emperature, orientationally ordered and high-temperature, orientationally d isordered or plastic phases of solid cubane are determined. The valence ban d of solid cubane is derived from the molecular states; the energy gap betw een the lowest unoccupied and highest occupied molecular orbital bands is r ather large due to the saturated carbon atoms. The effect of alkali-metal-a tom doping on the electronic energy bands is investigated. It is found that the metallic band of doped cubane is derived from the undoped solid cubane 's lowest conduction band with a significant contribution from the alkali-m etal atom.