| Mechanisms such as nanomechanics, changes in chemical structure, and van der Waals interactions are difficult to observe on the atomic scale by experimental methods. It is important to understand the fundamentals of these processes on a small scale to reach conclusions of results that are observed on a larger scale. Computational methods may be readily applied to investigate these mechanisms on models a few nanometers in dimension and the results can give insights to processes that occur during real time experiments. The classical molecular dynamics simulations here utilize the reactive empirical bond-order (REBO) or adaptive intermolecular REBO (AIREBO) potentials, to model short range behavior, coupled with the Lennard Jones potential (and torsion for AIREBO), to model long range interactions of carbon nanostructures and hydrocarbons.;The bond order term in the REBO/AIREBO potential allows for the realistic treatment of these materials as it correctly describes carbon (and silicon and germanium) hybridizations, and allows for bond breaking and reformation unlike basic molecular mechanics. This is a key feature for simulating irradiation and pullout mechanics on graphite and carbon nanotube and their composites.;The irradiation simulations on graphite, with the same conditions as the experimental irradiation of highly pyrolythic graphite, provide insight to the types of defects that were observed on a larger scale by Scanning Transmission Microscopy (STM) images. Experimental characterization from collaborators mapped out the surface of irradiated graphite while computational theory further described the defects and observed the evolution of the defects during the irradiation procedure.;Multi walled carbon nanotubes (MWNT) were irradiated with different particles to compare the effect that incident species have on the nanotubes' surfaces as well as the crosslink distribution of the radial cross sections. Irradiation is a common technique to modify the interfacial areas between the fiber and matrix to improve compatibility in polymer composites. Inducing crosslinks between shells of the MWNT by irradiation drastically decreased the sword in sheath deformation, where inner shells slip out with respect to outer shells, that was computationally demonstrated.;A similar procedure was also carried out on carbon nanotube - polystyrene composites. Argon irradiation was simulated for three different types of nanotubes: double-walled, single-walled, and a bundle of four single-walled nanotubes, in a polystyrene matrix. The polymer emission, depth of particle penetration, and nanotube pullouts were observed, it was shown that the presence of carbon nanotubes limited these processes.;Atomic Force Microscopy (AFM) and X-Ray Diffraction (XRD) images in conjunction with AIREBO molecular dynamics simulation trajectories of C60 and pentacene films of various ratios gave theoretical and experimental insight on the molecular evolution of donor and acceptor aggregation for optimizing the design of effective organic semiconductors.;Atomic-scale simulations are thus shown to be a powerful computational tool to better understand the properties of carbon nanostructures and hydrocarbons. This dissertation illustrates how effective they are for providing insight on chemical modification, nanomechanical deformation, and equilibration mechanisms on the atomic scale. |
