Simulations of field emission and dielectrophoresis using a monopole-dipole representation of carbon nanotubes

A model is presented to compute the polarization of carbon nanotubes, where each atom is described by both a net electric charge and a dipole. The model parameters are adjusted to reproduce the polarizability of C/sub 60/, C/sub 70/ as well as the transverse polarizability of (5,5), (6,6) and (9,0) nanotubes. The model gives a better account of the metallicity of these nanotubes that is essential for the modeling of field emission. An extension of the model is also presented, where discrete representation of carbon nanotube is combined with a dielectric-function representation of its environment. This technique provides a complete picture of the potential energy of systems made of carbon nanotubes and metallic elements, which can be applied to field-emission device.