Thermodynamic phase stabilities of nanocarbon

Despite the intense interest in nanocarbon for a variety of engineering applications, many details of their relative thermodynamic stabilities remain mysterious. Here, a unified thermodynamic model for the thermodynamic stabilities of nanocarbon in different polymorphs is presented based on energetic contributions of surface energy and surface stress on total Gibbs free energy of systems. Through considering thermodynamically size-dependent phase stabilities among graphite, diamond, fullerenes, and carbon onions, size–temperature phase diagram of nanocarbon is established. The equilibrium temperatures among these phases increase as their sizes decrease. The obtained results are consistent with the available experimental and theoretical results. Moreover, related phase stability of bucky diamond in comparison with above phases are also discussed.