Thermal vacancies in one-dimensional Xe adsorbate chains in grooves of nanotube bundles

The specific heat $C_P$ of quasi-one-dimensional Xe adsorbate chains in grooves on the outer surface of closed single-walled carbon nanotube bundles in the temperature interval of $2$–$55$ K has been measured. Experimental data have been compared to the theoretical $C_V$ values. The sharp increase in the difference $C_P-C_V$ above $30$ K has been explained within the model of formation of single thermal vacancies in the one-dimensional Xe adsorbate chains. The enthalpy, entropy, and concentration of thermal vacancies have been determined.