Dynamics of a bunch of carbon nano-tubes

Nano-diameter tubules made of folded graphitic sheets have drawn the attent ion of physicists ever since the advent of fullerene research. These are in teresting because of their conductivity (depends upon chirality) as well as their mechanical properties. Bunches of such tubes, single-walled and each of same diameter (similar to 14 Angstrom), have been produced in the labor atory. In this work we explore the mechanical properties of the bunch (hexa gonal packing), having assumed, for simplicity, uniform continuous distribu tion of carbon atoms on each tube. The atom-atom potential (6-exp) is of Ki taigorodsky type where only inter-tube interactions are considered. Intra-t ube interactions are not considered (implying a rigid tube model). This app roximation works very well for pure C-60 solid. We find that the range of e xternal modes is not well separated from the radial mode frequency of the s ingle tube as indicated by measured data. Therefore, interpretation of expe rimentally observed frequencies needs to be done in terms of total modes of the bunch, including internal as well as external modes. We have also stud ied pressure dependent deformations of such a bunch, which are found to be very interesting and are likely to provide information about their mechanic al strength.