Etude théorique des propriétés vibrationnelles de nanostructures carbonées planes et de défauts ponctuels dans les nanotubes de carbone

Abstract

The purpose of this thesis is to present a study of vibrational properties of plane carbon systems and of defects in carbon nanotubes. The method we use is based on the search for peaks in the local vibrational density of states (VDOS) with, as a final goal, their assignations to some particular features of the system (defects or edges). The VDOS are then calculated on some characteristic atomical sites by means of the recursion method in an harmonic formalism of the small amplitude oscillation theory. Firstly, a simple Born - von Kármán model fitted on the force constants of the perfect graphite is used in order to study nanotubes with or without defects. Our method is then made more consistent by using a semi-empirical atomical potential (REBO2) to directly calculate the force constants for each system after optimisation. Besides the characterization of several point defects likely to be found in tubes, we show the capability of REBO2 to predict coherent phonon modes in nanoribbons and nanotubes. Stone-Wales defect, vacancy, bivacancy, a pentagonal-heptagonal intermolecular junction, a capped nanotube, an isotopic defect and haeckelite structures are investigated in our framework.

Date of Award	2 Sept 2009
Original language	French
Awarding Institution	University of Namur
Supervisor	Philippe Lambin (Supervisor), Luc Henrard (Jury), Paul THIRY (President), Jean-Louis Sauvajol (Jury) & Hakim Amara (Jury)