Condensed phases of gases inside nanotube bundles

Abstract

An overview is presented of the various phases predicted to occur when gases are absorbed within a bundle of carbon nanotubes. The behavior may be characterized by an effective dimensionality, which depends on the species and the temperature. Small molecules are strongly attracted to the interstitial channels between tubes. There, they undergo transitions between ordered and disordered quasi-one dimensional (1D) phases. Both small and large molecules display 1D and/or 2D phase behavior when adsorbed within the nanotubes, depending on the species and thermodynamic conditions. Finally, molecules adsorbed on the external surface of the bundle exhibit 1D behavior (striped phases), which crosses over to 2D behavior (monolayer film) and eventually 3D behavior (thick film) as the coverage is increased. The various phases exhibit a wide variety of thermal and other properties that we discuss here.

Enhanced cohesion of matter on a cylindrical surface

“…The opposite limit, R approaching zero, is here called "lineland", a 1d limit. Matter in lineland has been explored for many years as an abstract problem [7] and has recently received particular attention in connection with the possible realization of 1d phases within interstitial channels or external surface grooves on nanotube bundles [2,8,9,10,11,12,13,14,15,16]. A logical question addressed in this paper is whether the properties of matter in "cylinderland" evolves smoothly (or even monotonically) between these limits as the value of R is varied.…”

“…The discovery of carbon nanotubes has stimulated a rapid evolution of ideas, experiments and understanding concerning states of matter confined to the proximity of a cylindrical surface [1,2,3]. Examples of such systems include electrons present within a nanotube and atoms or molecules moving just outside or within such tubes.…”

Quantum dynamics of a hydrogen molecule confined in a cylindrical potential

“…The study of quantum dynamics of hydrogen molecules in confined geometries has recently developed into an active field both experimentally and theoretically [1][2][3][4][5][6][7][8][9][10][11][12] due to potential use as catalysts, molecular sieves, and storage media. In the case of fullerenes and nanotubes, such trapping may yield new exotic quantum systems due to zero and one dimensionality of the absorption sites, respectively.…”

Thermodynamic properties and correlation functions of Ar films on the surface of a bundle of nanotubes

“…Further adsorption at low temperature (T ) is predicted to manifest a so-called three-stripe phase of gas aligned parallel to the grooves. 21 At higher gas coverage (N ), there occurs a two-dimensional monolayer phase, qualitatively analogous to that found on the graphite surface. 22,23 At even higher coverage, a multilayer film grows as P increases.…”