First-principles study of the stability of calcium-decorated carbon nanostructures

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 ͑DFT͒ 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 ͑CNT͒ as function of doping concentration. In graphene, we predict the existence of an equilibrium ͑ ͱ 3 ϫ ͱ 3͒ R30°commensurate CaC 6 monolayer that remains stable without clustering at low and room temperatures. For carbon nanotubes, we demonstrate that uniformly Ca-decorated zigzag ͑n Յ 10, 0͒ CNT become stable against clustering at moderately large doping concentrations while Ca-coated armchair ͑n , n͒ CNT exhibit a clear thermodynamic tendency for Ca aggregation. In both Ca-doped graphene and CNT systems, we estimate large energy barriers ͑ϳ1 eV͒ 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-d orbitals hybridization near the Fermi energy level.

Accuracy of density functional theory in the prediction of carbon dioxide adsorbent materials

“…the case of Cacoronene [14]). In consequence of these differences, hybridization between sd-sorbent and p-CO 2 orbitals leading to strong gas attraction will be more limited in Ca-C 14 H 10 complexes than in Ca-decorated graphene [21].…”

“…Consequently, computational accuracy tests need to be performed in scaleddown systems resembling to the structure and composition of the material of interest (e.g. the case of organic C n H m molecules to graphene [12][13][14][15]). Generalization of so-reached conclusions to realistic systems however may turn out to be fallacious since intrinsic DFT limitations (e.g.…”

Polylithiated (OLi2) functionalized graphane as a potential hydrogen storage material

“…Alkali metals can be a good dopant on carbon nanostructures owing to its low cohesive energy (E coh ~1eV) 8 and uniform distribution on surface.…”

“…Different storage media were considered for efficient H 2 storage in recent past and carbon based nanostructures are considered to be the most promising materials. [6][7][8][9] Along with the other countless applications, carbonaceous nanomaterials including fullerenes, carbon nanotubes (CNTs), graphene etc. have extensively been used for energy applications, especially hydrogen storage purposes.…”

Strain-induced stabilization of Al functionalization in graphene oxide nanosheet for enhanced NH3 storage

“…1, [14][15][16][17] For a maximal utility of the functionalization, it needs to meet these two ends concurrently: (1) the binding of the dopant to the nanomaterial needs to be stable and (2) the functionalization is intended to be as effective as possible. 17 Weak binding of metal atoms to the substrates is still frequently encountered, 14,15,18 which brings down the utility of the functionalization.…”