Density Layering During Gaseous Diffusion in Carbon Nanotubes: An Analytic Model

Recently, molecular dynamics simulations have predicted that concentric layers of gaseous carbon dioxide particles will appear in carbon nanotubes. We show in this letter how this effect can be predicted analytically by considering the potential field generated by the pore wall. The layer potential expression thus derived can be used to reproduce the essential features of a particular MD study of gaseous carbon dioxide within a (40, 40) carbon nanotube and confirm, from an energetic point of view, that an outer gaseous layer will be stable. With a closed form expression for the layer potential known, we are able to derive formulas for quantities typically of interest in a Lennard-Jones analysis, such as minimum energy, equilibrium position and the location of zero potential.