Carbon tubes discussed in a metallic ring model

The similarity of the anisotropic properties of large diameter carbon tubes in a magnetic field to the anisotropy of graphite, suggests the use of a free electron model to describe their electronic structure in terms of the graphite band model. The diamagnetism of carbon tubes is discussed in terms of a model which accounts for the tubular deformation of graphite planes using the vector pseudo-potential: A(d) = h rho(2).[-y, x, 0], where rho is the radius of the tube orientated along the z-axis. The deformation of the plane splits the energy band in two with opposite angular momentum, confinement on the tube excludes Landau quantization, and instead the field generates a net ring current. (C) 1997 Elsevier Science Ltd.