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Abstract: First-principle calculations using quantum-mechanical density functional theory are carried out to study nitrogen incorporation in amorphous carbon, in which the structural models from liquid quench containing 64 atoms are introduced. The properties simulated for N incorporated amorphous carbon are in agreement with the available experimental results. The topological and electronic properties for nitrogen incorporation structures with various densities are investigated, and it is found that the bonding configuration of nitrogen atoms strongly depends on the density and the nitrogen concentration in the network. The simulations provide a qualitative support for a low nitrogen doping efficiency observed in the experiment since no true doping (N atoms substitutionally occupy C sites, leading to a donor level below conduction band mobility edge E c ) exists in any cases studied. For the tetrahedral amorphous carbon (at density of 2.9 g/cm3) with a low concentration of nitrogen (1.6 at% and 3.2 at%), the incorporated N atoms are found to adopt the auto-compensated sites or to be in threefold coordination. In particular, a new threefold C defect is found, which is introduced by nitrogen auto-compensation. Nitrogen incorporated amorphous carbon (2.0 g/cm3) leads to the formation of a graphite-like structure with twofold nitrogen coordination. [Copyright &y& Elsevier]

Abstract: The combination of PM3 semi-empirical method for geometry optimization, and ab initio DFT (density functional theory) for energy calculation, is used to study the configurations of hydrogen molecules at 0K within the vacuum of C60 fullerene and carbon nanocapsules. The obtained structural information including the molecular arrangement and structural state of the clusters of H2 are mainly determined by two kinds of repulsive energies, namely that between the H2 molecules and the wall of the spheroidal or capsule like carbon structure, and that between interacting H2 molecules. It is further established that the repulsive energy among the H2 molecules is not purely a function of the number of encapsulated H2, and there is a tradeoff between the two kinds of repulsive energies. [Copyright &y& Elsevier]

Catalytic graphitization of carbon laminations was carried out using mesocarbon microbeads as the matrix precursor. Aqueous tape casting was used to prepare the carbon laminations, which were doped separately with Ti, ZrO2 and B4C powders. After sintering at 1400 °C in a vacuum, these dopants were found to enhance the degree of graphitization and improve the properties of the laminations. Ti was the most effective catalyst of the three dopants. The effects of binary dopants on the graphitization process and properties of the resulting laminations were also tested, but the catalytic effect of binary dopants was found to be less than that shown by single additives. [Copyright &y& Elsevier]