Journal
PHYSICAL REVIEW B
Volume 82, Issue 15, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.82.155454
Keywords
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Funding
- European Commission [HPC08HF3RD-203]
- EPSRC SUPERGEN Initiative [GR/S26965/01, EP/E040071/1]
- Platform [GR/S52636/01, EP/E046193/1]
- EPSRC [EP/E046193/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [GR/S52636/01, EP/E046193/1] Funding Source: researchfish
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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 (root 3 x root 3) R30 degrees commensurate CaC6 monolayer that remains stable without clustering at low and room temperatures. For carbon nanotubes, we demonstrate that uniformly Ca-decorated zigzag (n <= 10, 0)CNT become stable against clustering at moderately large doping concentrations while Ca-coated armchair (n, n) CNT exhibit a clear thermodynamic tendency for Ca aggregation. In both Ca-doped graphene and CNT systems, we estimate large energy barriers (similar to 1 eV) for atomic aggregation processes, which indicates that Ca clustering in carbon nanosurfaces may be kinematically hindered. Finally, we demonstrate via comparison of DFT and Moller-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 pi-d orbitals hybridization near the Fermi energy level.
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