Abstract
In view of the interest in calcium-decorated carbon nanostructures motivated by potential biotechnological and nanotechnological applications, we have carried out a systematic and thorough first-principles computational study of the energetic and structural properties of these systems. We use density-functional theory (DFT) and ab initio molecular dynamic simulations to determine minimum energy configurations, binding energy profiles and the thermodynamic stability of Ca-decorated graphene and carbon nanotubes (CNT) as function of doping concentration. In graphene, we predict the existence of an equilibrium commensurate monolayer that remains stable without clustering at low and room temperatures. For carbon nanotubes, we demonstrate that uniformly Ca-decorated zigzag CNT become stable against clustering at moderately large doping concentrations while Ca-coated armchair CNT exhibit a clear thermodynamic tendency for Ca aggregation. In both Ca-doped graphene and CNT systems, we estimate large energy barriers for atomic aggregation processes, which indicates that Ca clustering in carbon nanosurfaces may be kinematically hindered. Finally, we demonstrate via comparison of DFT and Møller-Plesset second-order perturbation calculations that DFT underestimates significantly the weak interaction between a Ca dopant and a coronene molecule, and also that the Ca-coronene system is not physically comparable to Ca-doped graphene due to lack of electronic orbitals hybridization near the Fermi energy level.
4 More- Received 29 June 2010
DOI:https://doi.org/10.1103/PhysRevB.82.155454
©2010 American Physical Society