Phonons and specific heat of neon and methane on the surface of a nanotube bundle

Adsorbed Ne and CH₄ on the external surface of a nanotube bundle form quasi-one-dimensional phases at low temperature. This paper presents a study of the phonon spectra and the specific heat associated with these phases. For Ne, two groove phases of different density are investigated, while for CH₄ two groove phases of different density and the “three-stripe” phase are studied. In addition, results from classical Monte Carlo simulations are presented which provide information about the thermodynamic behavior of different phases of CH₄ at higher temperatures; a dimensionality crossover is indicated by the presence of a distinctive peak in the specific heat.