Formulation in terms of normalized propagators of a charge-dipole model enabling the calculation of the polarization properties of carbon nanotubes and fullerenes

We present a model for the calculation of the polarization properties of fullerenes and carbon nanotubes. This model describes each atom by both a net electric charge and a dipole. Compared to dipole-only models, the consideration of electric charges enables one to account for the displacement of free electrons in structures subject to an external field. It also enables one to account for the accumulation of additional charges. By expressing the electrostatic interactions in terms of normalized propagators, the model achieves a better consistency as well as an improved stability. In its most elementary form, the model depends on a single adjustable parameter and provides an excellent agreement with other experimental and theoretical data. The technique is applied to a C720 fullerene and to open and closed (5,5) nanotubes. The simulations demonstrate the improved stability of our algorithm. In addition, they quantify the role of free charges in the polarization of these structures. The paper finally investigates the field-enhancement properties of open and closed (5,5) nanotubes.