Density distributions of diatoms in carbon nanotubes: A grand canonical Monte Carlo study

Grand canonical Monte Carlo simulations have been carried out for dumbbell (D) and spherical (S) models of N-2 and Br-2 in single-walled carbon nanotubes, with nanotube radii ranging from 4.029 to 25.142 Angstrom. The radial density distributions between models S and D in the nanotube were compared under similar bulk conditions. For gas and liquid bulk densities of N-2, differences between the pore density distributions for the S and D models in the nanotube were small and the inclusion of quadrupole moments to model D had little effect. In contrast, the density distributions between the S and D models for Br-2 showed greater differences for the bulk liquid case. Angular density distributions show that molecules adjacent to the nanotube wall orient parallel to the wall. At high densities the wall layer contains a mixture of wall-parallel and wall-perpendicular orientations, giving rise to a shoulder in the density distributions for Br-2. (C) 1998 American Institute of Physics.