The high conductivity of defect fullerene C40 cage

Using the first-principles methods, density-functional theory (DFT) and Hartree–Fock (HF), we have studied the defect fullerene cages by removing C2 units from icosahedral C60, sequentially down to C30. It is found that the band gap of defect fullerenes depends on the size considerably, and is shown for the first time that C40 cage can have very small energy gap. Also, we have investigated forty isomers of C40 cage and have selected ones with low energies and high conductivities. Therefore C40 is proposed to be an interesting unit for nanodevice applications.