A comparative investigation on electronic structures and optical properties of C60 polymers, periodic fulleriods and carbon nanotubes

We present systematically theoretical investigations on electronic and optical properties of quasi-one-dimensional (1D) all-carbon materials: C60 polymers (CP), periodic peanut-shaped fulleriods (PPSF) and armchair (5,5) carbon nanotubes (CNTs) to understand structure-property relationships. Their electronic structures and optical absorption spectra are calculated by the first-principles density functional theory and the random phase approximation (RPA). It is found that the system structures and sizes play a vital role on their physical properties so that three systems show distinctively different electronic and optical behaviors. CP and PPSF exhibit finite energy-band gaps while (5,5) CNTs are found metallic. Unlike C60 polymers and PPSF, whose optical properties are converged with a few of C60 units, the optical spectra of CNTs depend very much on the tube length and the converged optical properties of CNTs are not observed even for the tube as long as 100 Å due to the overall delocalized π-electrons. The optical properties of infinite long systems have been predicted by the finite-size calculations. The relation between the geometrical structures and electronic properties have been quantitatively established.