  The heat capacity of 1D chains of Xe adsorbed in the outer grooves of bundles
of closed single-walled carbon nanotubes have been investigated in the
temperature range from 2 to 55 K. The experimental results of heat capacity are
close to the theoretical calculation below 8 K. Above 8 K the experimental
curve exceeds the theoretical one and excess increases monotonously with
temperature. It was assumed that the sharp increase of the difference between
the experimental and theoretical curves of heat capacity above 30 K is
associated with the occurrence of the thermally created vacancies in the chains
due to spatial redistribution of the xenon atoms. The molar enthalpy of vacancy
formation in the chain has been calculated.
