Squeezing carbon nanotubes

In this paper we briefly review the high pressure Raman studies. on single and double walled carbon nanotubes focussing on the perssure dependence of the low frequency radial breathing vibrational modes. Previous work on single walled carbon nanotube bundles have shown that the normalized pressure-induced frequency shift, Phi = (1/omega(R)) (domega(R)/dP) similar to D-2 where omega(R) is the radial mode frequency and D is the nanotube diameter. We show here that the R-modes due to the inner tubes in double walled carbon nanotubes, have a very small, diameter independent value for Phi, as predicted for the case of isolated tubes.