  The specific heat at constant pressure of bundles of single-walled carbon
nanotubes closed at their ends has been investigated in a temperature interval
of 2-120 K. It is found that the curve of heat capacity has features near 5,
36, 80, and 100 K. The experimental results on the heat capacity and the radial
thermal expansion coefficient of bundles of SWNTs oriented perpendicular to the
sample axis have been compared. It is found that the curves of the heat
capacity and the radial thermal expansion coefficient exhibit a similar
temperature behavior above 10 K. The temperature dependence of the Gruneisen
coefficient has been calculated. The curve of the Gruneisen coefficient also
has a feature near 36 K. Above 36 K the Gruneisen coefficient is practically
independent of temperature. Below 36 K the Gruneisen coefficient decreases
monotonically with lowering temperature and becomes negative below 6 K.
