Trends in the Adsorption of 3d Transition Metal Atoms onto Graphene and Nanotube Surfaces: A DFT Study and Molecular Orbital Analysis

Abstract

The functionalization of graphene and (8,0) single-walled carbon nanotubes (SWCNTs) with individual 3d transition metal (TM) atoms was modeled using density functional theory (DFT) calculations. The structural geometry, magnetism, and binding energies were analyzed in terms of the density of states (DOS), Bader charges, and organometallic M(η 6 -C 6 H 6 ) orbital molecular models. Trends in the binding energies were explained by a model, which included several contributions from the chemisorbed atoms: Coulomb interaction, 3d n 4s x f 3d n+x electronic promotion energy (EPE), and occupation of the 1e 2 (δ), 2e 1 (π), and 2a 1 (σ) metal orbitals. 4s occupation, which causes Pauli repulsion, explained the physisorption trends of Cr, Mn, and Cu. The model was successfully extrapolated to a convex surface, such as that of (8,0) SWCNTs. The potential energy surfaces for the adatoms adsorbed on graphene were determined to evaluate the diffusion energy barriers. We found that Sc, Ti, Fe, and Co metals could be isolated on the graphene surface, whereas all other 3d TM atoms diffused (with possible aggregate formation).

On the structure and normal modes of hydrogenated Ti-fullerene compounds

“…In order to provide some confidence about the studied C 60 TiH n compounds, we have calculated the binding energies for the Ti atom on the C 60 , where the Ti atom is bound to (6,6), (5,6), hexagonal and pentagonal sites. The difference between the more stable (6,6) and the (5,6) site for the C 60 Ti structures is 0.58 eV, in contrast with a previous calculation by Valencia et al (2010) that mention that a 0.3 eV value is sufficient to hold one single Ti atom and to avoid the diffusion and therefore the clustering. It is important to mention here that the difference in energy between the (6,6) and (5,6) sites has to be considered as an indicative energy barrier of possible diffusion path to the Ti atom, within the quasiharmonic approximation.…”

“…Recently, a study of single transition-metal atoms laying on graphene and on a (8,0) single-wall carbon nanotube (SWCNT) has made clear that the clustering of the transition metal atoms depends on factors such as low metal binding energy and low diffusion barriers (Valencia et al 2010). While these factors determine the clustering of Ti atoms specifically on graphene and SWCNT with a large diameter (Krasnov et al 2007), it is likely that the same will occur on C 60 , but in this case the small diameter and large curvature of C 60 would difficult the clustering and would make the fullerene a suitable candidate as substrate for transition metals.…”

First-principles Study of Electronic and Magnetic Properties of Manganese Decorated Graphene

“…This implies that the adsorption of Mn atom on graphene sheet with 18 or more number of carbon atoms is no more size-dependent. The magnitude of adsorption energy of Mn comparing to that for other adatoms shows that Mn is weakly bound on graphene, and the conclusion is consistent with the previous result [e.g., Valencia et al, 2010]. The present calculations reveal that the van der Waal's interaction plays vital role for such type of weak binding.…”

“…The adsorptions of some of the alkali and transition metal atoms on graphene have been already considered (at this department and outside) to study their geometrical and electronic properties [e.g., Pantha et al, 2014;Belbase, 2013;Khaniya, 2013;Lamichhane et al, 2014;Valencia et al, 2010;Chan et al, 2008]. The works reveal changes in their geometrical and electronic structure upon the adsorption of metal atoms, intending their further applications like in energy storage.…”

Chern insulators without band inversion in MoS2 monolayers with 3d adatoms

“…The total magnetic moment of each adsorption system with the most stable configuration can be rationalized by the valence electron configuration of the TM atom after the adsorption ( Table I). Note that the interactions from the MoS2 ML make the electrons transfer from 4s into 3d states for the V, Mn, and Fe systems, as also reported in graphene with some TM adatoms [30]. Thus, the total magnetic moment of V is very large (5.0 µB), while that of Fe is very small (2.0 µB ).…”