First Principles Study Of Transition Metal Diatomics As The First Step In Multiscale Simulations Of Carbon Nanotube Growth Process

Single wall carbon nanotubes (SWNT) are cylindrical molecules with unique properties that make them potentially useful in wide variety of applications, including nanoelectronics and photonics. However, these applications are feasible only if SWNTs have specific chirality. Much work remains to be done to gain control over selectivity of SWNT synthesis by chemical vapor deposition (CVD). One of the prime factors affecting the chirality of SWNT is the chemical nature and rate of carbon containing feed gas. Mechanistic kinetics study of CVD processes are gravely complicated by variety of the species involved and by the high temperatures of the reaction chamber. It is not probably feasible to extract the information on mechanism for SWNT synthesis from experimental data. The chemical origin of the reaction barriers and intermediates, however, could be analyzed using molecular simulations. High theory level can be used for di- and tri-atomic fragments, and generate parameters for bond order force field. In turn, force field simulations will be used to characterize intermediates and transition states, and calculate rate constants. Here we propose multiscale computer modeling of CVD process. Our approach is to extract the structure of the intermediates from molecular dynamics trajectories, conduct the transition state search, predict the free energy activation barriers and the rate constants, build the kinetic model of the growth process, and implement it in kinetic Monte Carlo algorithm to predict the optimal experimental conditions necessary to produce desired chirality of SWNT