Adsorption of Gold atoms on carbon nanotubes
Antônio J. R. da Silva, J. Carrijo Faria, Edison Z. da Silva, and A. Fazzio
Instituto de Fisica - Universidade de Sao Paulo, BR
Keywords: Carbon nanotubes, adsorption of atoms on carbon nanotubes, gold
We study in detail the adsorption of Au on single walled carbon nanotubes (SWCN). All our results are based on ab initio total energy Density Functional Theory calculations using numerical orbitals as basis sets. We have used the SIESTA code, which performs a fully self-consistent calculation solving the Kohn-Sham equations. In particular, we have studied in great detail the interaction of a single gold atom and a dimer of Au atoms with a metallic (6,6) SWCN. For the single gold atom, the lowest energy adsorption sites are on top of the C atoms (DT sites), and there is a maximum in the potential energy surface for adsorption of a single Au atom at the center of a hexagon in the tube wall (HC site). The energy difference between the DT sites and the HC site is approximately 0.35 eV. The barrier to migrate between two DT sites along the C-C bond is of approximately 0.1 eV. Therefore, at room temperature, we can conclude that the Au atoms will migrate quite easily along the C-C bonds. The binding energy for a gold atom at a DT site is of the order of 1.2 eV, smaller than the binding energy between two Au atoms at the surface (» 1.9 eV). There are many configurations for a Au dimer to adsorb on the (6,6) SWCN, all of them with dimer binding energies to the tube of the order of 1 eV. Finally, larger structures, like trimers, will also be discussed.
NSTI Nanotech 2003 Conference Technical Program Abstract