Abstract
Using the first-principles methods, density-functional theory (DFT) and Hartree-Fock (HF), we have studied the defect fullerene cages by removing C-2 units from icosahedral C-60, sequentially down to C-30. It is found that the band gap of defect fullerenes depends on the size considerably, and is shown for the first time that C-40 cage can have very small energy gap. Also, we have investigated forty isomers of C-40 cage and have selected ones with low energies and high conductivities. Therefore C-40 is proposed to be an interesting unit for nanodevice applications. (C) 2009 Elsevier B.V. All rights reserved.