| LDF CALCULATIONS OF POINT DEFECTS IN GRAPHITES AND FULLERENES (2008) | |||||||||||||
Abstract | |||||||||||||
| Using a spin density functional code (AIMPRO) we have examined the properties of interstitials and adatoms on graphite (modelled as one, two or three layers of a polyaromatic hydrocarbon C62H20) and on a number of fullerenes. We report the structure, bonding and energetics of these defects and give anaccount of their mobilities. Their formation energies are high and properties are spin-dependent, making parametrised potentials and simpli ed tight binding schemes inappropriate. For the adatom we ndavery mobile triplet state in which the carbon atom is partially ionically bound and a singlet state in which the atom is located above a C{C bond center. For the interstitial we nd a structure analogous to spiro-pentane in which the interstitial forms 1 two almost equilateral triangular rings with pairs of carbon atoms in adjacent layers. A model presented earlier for the structure of quasi-spherical carbon onions requires that the autocatalysis mechanism for Stone-Wales transformations be catalysed by carbonadatoms.We therefore present calculations of the activation energies for these catalysed processes as a function of substrate (graphite/fullerene) curvature to extend the earlier workonC60. | |||||||||||||
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