Size-dependent polarizabilities of finite-length single-walled carbon nanotubes

Polarizabilities of single-walled carbon nanotubes with length up to 13.5 nm are studied by systematic semi-empirical PM3 calculations. Longitudinal polarizabilities increase exponentially with increasing length and about 10% higher in zigzag tubes than in armchair tubes, at least in the calculated range. The chirality-dependence of the longitudinal polarizability in finite-length nanotubes is much weaker than that in infinite-length tubes. The transverse polarizabilities of nanotubes always increase linearly with increasing length, but they are independent of chiralities and energy gaps.