Abstract
To a large extent, the chemical and physical properties of carbon nanotubes and nanofibers are determined by their internal structure. Unfortunately, a fundamental understanding of the processes that drive structure determination is missing, thereby hindering the development of controlled synthesis strategies. Here we use theoretical calculations to analyze the time evolution of the shape of the interface between the catalyst nanoparticle and its associated graphitic nanofiber at the initial stages of growth. This phenomenological description of the behavior of the catalyst nanoparticle-graphite interface constructed with model parameters provides an understanding of the mechanisms that control the internal structure of carbon nanofibers. We show that during growth the interface loses stability if the magnitude of the interface curvature exceeds a critical value cappa_crit, and as a result a cavity forms in the center of the nanofiber.