  We study the behaviour of the C60 molecule under very high internal or
external pressure using Tersoff as well as Brenner potentials. As a result, we
estimate the critical internal and external pressures that lead to its
instability. We also calculate stretching force constant and bulk modulus of
this molecule at several pressures under which the molecule remains stable. The
values of these estimated here at zero pressure agree closely with those
obtained in earlier calculations. We also observe that at high pressures, a
finite value of parameter of Tersoff potential gives physically acceptable
results in contrast to its value zero, which is usually taken for the carbon
systems.
