Electronic structure simulations of carbon nanotubes

Recently, Iijima et al. (Nature, 363 (1993) 603) and Bethune et al. (Nature, 363 (1993) 605) have found carbon-are conditions that yield extended single-shell nanometer-diameter carbon fibers. The individual hollow concentric graphitic tubules which comprise these fibers can be visualized as constructed from rolled-up single sheets of graphite. We have examined both the electronic and structural properties of these materials using a first-principles, self-consistent, all-electron Gaussian-orbital-based local-density functional (LDF) approach. As part of these studies, we have calculated the optical absorption spectra of several representative nanotubes using an Ehrenreich-Cohen perturbation-theory approach using the LDF electronic structure results. We discuss these results in the light of recent experimental results for electron energy-loss spectra of these novel materials.