Shear strain in carbon nanotubes under hydrostatic pressure

We investigated the hydrostatic and shear strain components introduced in the graphite hexagons by applying hydrostatic pressure to single-walled carbon nanotubes. The vibrational modes are expected to show different pressure derivatives depending on the polarization of the eigenvector with respect to the nanotube axis, hut independent of chirality. A comparison with tight-binding calculations allows us to estimate the Gruneisen parameter (1.24) and the shear phonon deformation potentials (0.41); they compare favorably with experimental results on nanotubes.