van der Waals interaction in nanotube bundles: Consequences on vibrational modes

Abstract

We have developed a pair-potential approach for the evaluation of van der Waals interaction between carbon nanotubes in bundles. Starting from a continuum model, we show that the intertube modes range from 5 ${\mathrm{cm}}^{-1}$ to 60 ${\mathrm{cm}}^{-1}.$ Using a nonorthogonal tight-binding approximation for describing the covalent intratube bonding in addition, we confirm a slight chiral dependence of the breathing mode frequency and we found that this breathing mode frequency increases by $\sim 10\%$ if the nanotube lies inside a bundle as compared to inside the isolated tube.