A Monte Carlo study of C70 molecular motion in C70@SWCNT peapods

We present Monte Carlo simulations of chains of C-70 molecules encapsulated in a single-walled carbon nanotube (SWCNT). For various tube radii R (6.5 angstrom <= R <= 7.5 angstrom), we analyze rotational and translational motion of the C-70 molecules, as a function of temperature. Apart from reproducing the experimentally well-established lying and standing molecular orientations for small and large tube radii, respectively, we observe, depending on the tube diameter, a variety of molecular motions, orientational flipping of lying molecules, and the migration of molecules resulting in a continual rearrangement of the C-70 molecules in clusters of varying lengths. With increasing temperature, the evolution of the pair correlation functions reveals a transition from linear harmonic chain behavior to a hard-sphere liquid, making C-70@SWCNT peapods tunable physical realizations of two well-known one-dimensional model systems. (C) 2011 Elsevier Ltd. All rights reserved.