Statistical mechanics and structural properties of carbon(60) molecules inside carbon nanotubes

Miroslav Hodak, University of Pennsylvania

Abstract

In this thesis, we theoretically investigated energetical, thermodynamical and structural properties of C60 peapods. The energetics calculations were based on assuming the Lennard-Jones interaction potential between carbon atoms on surfaces of interacting molecules. The interaction energy for various arrangements of a C60 and a (10,10) nanotube was calculated. It was concluded that the most stable configuration is when a C60 molecule is inside the nanotube. The investigation of lattice properties of (10,10) nanotube ropes filled with C60 molecules showed that compared to the lattice of unfilled nanotube ropes, the cohesive energy is larger by 15%, the bulk modulus is increased by 10%, while the equilibrium spacing is almost unchanged. The calculation of optimum and maximum sizes of fullerenes inside nanotubes yielded simple criteria for determining radii of spherical fullerene molecules that can fill nanotube with given radius. Similar criteria for ellipsoidal fullerenes and multi-walled nanotubes were also obtained. The structures formed by C60 molecules inside nanotubes with various radii were studied using the simulated annealing technique. It was found that for nanotube radii from 6.27 Å to 13.57 Å ten different phases exist. Both chiral and achiral phases were found. The achiral phases consist of layers of stacked polygons rotated by an angle of 360/(2 k) relative to each other, where k is an integer. The chiral phases consist of multi-stranded helices. Three statistical mechanical methods were used to study the thermodynamic properties, structure and clustering of systems with various concentrations of C60 molecules inside nanotubes. These were the lattice gas model, the configuration integral method and the Monte Carlo calculations. These gave results for both open and closed nanotubes systems of finite and infinite length. For all systems, the possibility of phase transition was also investigated.

Subject Area

Materials science|Molecules

Recommended Citation

Hodak, Miroslav, "Statistical mechanics and structural properties of carbon(60) molecules inside carbon nanotubes" (2002). Dissertations available from ProQuest. AAI3073010.
https://repository.upenn.edu/dissertations/AAI3073010

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