Elastic properties of carbon nanotubes under hydrostatic pressure

We present first-principles calculations of the bulk and linear moduli of carbon nanotube bundles and individual tubes. The calculations were done using the local-density approximation of density-functional theory. We found the bundle bulk modulus (37 GPa) to be essentially the same as that of graphite (between 34 and 42 GPa experimentally). The elastic properties of the individual tubes in the bundles are excellently described by the elastic continuum approximation. The linear modulus along the nanotube axis is 1. 5--2 higher than the radial modulus for nanotube radii between 0. 8 and 1. 4 nm.