Microscopic determination of the interlayer binding energy in graphite

High-tensile-strength carbon nanotubes are nonetheless susceptible to large radial deformations. In particular, tubes may collapse so that opposing tube walls attain the graphitic interlayer spacing. A simple elastic model shows that the ratio of mean curvature modulus to the interwall attraction of graphite determines the cross-section of a collapsed tube. Transmission electron microscopy of collapsed tubes confirms the elastic model and affords the first microscopic measurement of the strength of the intersheet attraction, a quantity otherwise difficult to assess.