Diameter distribution of single wall carbon nanotubes in nanobundles

The frequency of the Raman active Ale radial breathing mode has been widely used as a tool to estimate the distribution of diameters of single wail ca rbon nanotubes (SWNT). However, the relation between frequency and diameter is not straightforward and results are model-dependent. Because most of th e experiments are performed on bundles and not on isolated tubes, the model should especially take into account the van der Waals inter tube interacti ons. Here. we use a pair-potential approach to account for such interaction s and we derive a nonlinear relation between the SWNT diameter and the freq uency of the A(1g) radial breathing modes. We demonstrate a good agreement between calculations and the diameters derived from diffraction experiments on the same samples.