  We report the results of a model calculation for studying the effects of
hydrostatic pressure on a bunch of carbon nanotubes. At pressures that we work
with, the deformation in axial direction comes out to be negligibly small. We
find that hydrostatic pressure is an ideal probe to study the radial
deformations of the nanotubes. The nanotubes are considered to be flexible,
identified by a flattening of cylinders under pressure through a parameter f.
We use the 6-exponential and Brenner potentials to account for inter and
intra-tube interactions respectively. We calculate the total energy of the
deformed tubes in bunches. The free energy thus calculated enables us to
calculate phase changes at various pressures. From our calculations, we find
the phase transformation to occur at about 5GPa.
