Transition metal adatoms on graphene: A systematic density functional study

Manadé, Montserrat; Viñes, Francesc; Illas, Francesc

doi:10.1016/j.carbon.2015.08.072

Cited by 165 publications

(196 citation statements)

References 80 publications

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“…However, we do note small changes in the metal-carbon or metalboron/nitrogen bond length upon an increase in system size. The adsorption sites here compare well with those of earlier investigations [3,5,16].…”

Section: Resultssupporting

confidence: 88%

“…Prior to creating the super-cells for the adsorption studies, the dimensions of each nanotube (NT) unit cell and the graphene sheet are optimized. The obtained parameter with respect to the growth direction (c) of the nanotubes are: 0.252 nm for the (5,5) BNNT, 0.247 nm for the (5,5) CNT and 0.428 nm for the (8,0) CNT, respectively. In the case of graphene, the a and b lattice parameters are found to be 0.247 nm.…”

Section: Methodsmentioning

confidence: 99%

“…Among the latter are many density functional theory (DFT) studies examining the behavior of single metal atoms. These, however, show variation in the binding strengths up to several electron volts [5]. In part, this is due to differences in the methods employed, such as spin-polarized versus non-spin-polarized calculations, ultrasoft pseudo-potentials versus projector augmented wave methods (PAWs), or the use of LDA versus GGA exchange functionals.…”

mentioning

confidence: 99%

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Metal adsorbate interactions and the convergence of density functional calculations

Rohmann

Ochoa

Zwolak

2020

The Journal of Chemical Physics

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The adsorption of metal atoms on nanostructures, such as graphene and nanotubes, plays an important role in catalysis, electronic doping, and tuning material properties. Quantum chemical calculations permit the investigation of this process to discover desirable interactions and obtain mechanistic insights into adsorbate behavior, of which the binding strength is a central quantity. However, binding strengths vary widely in the literature, even when using almost identical computational methods. To address this issue, we investigate the adsorption of a variety of metals onto graphene, carbon nanotubes, and boron nitride nanotubes. As is well-known, calculations on periodic structures require a sufficiently large system size to remove interactions between periodic images. Our results indicate that there are both direct and indirect mechanisms for this interaction, where the latter can require even larger system sizes than typically employed. The magnitude and distance of the effect depends on the electronic state of the substrate and the open-or closed-shell nature of the adsorbate. For instance, insulating substrates (e.g., boron nitride nanotubes) show essentially no dependence on system size, whereas metallic or semi-metallic systems can have a substantial effect due to the delocalized nature of the electronic states interacting with the adsorbate. We derive a scaling relation for the length dependence with a representative tight-binding model. These results demonstrate how to extrapolate the binding energies to the isolated-impurity limit.Graphene, carbon nanotubes (CNTs), and boron nitride nanotubes (BNNTs) have exceptional mechanical, thermal, and electronic properties. These materials are thus the subject of intense research. Adsorption studies range from hydrogen and fluorine to metals of the 3d, 4d, and 5d series [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Among the latter are many density functional theory (DFT) studies examining the behavior of single metal atoms. These, however, show variation in the binding strengths up to several electron volts [5]. In part, this is due to differences in the methods employed, such as spin-polarized versus non-spin-polarized calculations, ultrasoft pseudo-potentials versus projector augmented wave methods (PAWs), or the use of LDA versus GGA exchange functionals. However, even studies employing almost identical techniques yield different results. For example, comparing the investigations of Manadé et al. [5], Pašti et al. [3] and Liu et al. [7] with respect to 3d metal adsorption, which all employed the same computational package, the (GGA-PBE) exchange-correlation functional, and PAWs, as well as a 4 × 4 graphene super cell, there are differences of up to 0.56 eV.Here, we investigate the binding energy dependence on the system size for various 3d metals on graphene, CNTs, and BNNTs by means of DFT. We aim to identify the cell size required to obtain, or extrapolate to, the isolated impurity limit, as well as understand related sources of error. Up...

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Section: Resultssupporting

confidence: 88%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Metal adsorbate interactions and the convergence of density functional calculations

Rohmann

Ochoa

Zwolak

2020

The Journal of Chemical Physics

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“…However, it surely depends in part on the site-dependent binding energies, which have been calculated by density functional theory. [21,26,27] While K and In are both most strongly bound at the hollow site of the graphene honeycomb, they have Figure 7. Resistance versus V g during warmup from 2 to 200 K in a third device after Os deposition.…”

Section: Resultsmentioning

confidence: 99%

“…This is rather lower-and of opposing sign-than the 0.3 − 0.6 electrons per atom expected from DFT calculations. [21,26,27] One possibility for the low doping efficiency is that the Os adatoms form clusters upon landing on the graphene. The atoms are evaporated from a hot W wire with a temperature approaching 3000 K, [39,46] and likely cool by emission of phonons in the graphene, during which the adatom is able to traverse the surface.…”

Section: Os Adatom Densitymentioning

confidence: 99%

Unexpected Hole Doping of Graphene by Osmium Adatoms

Elias

Henriksen

2019

Annalen der Physik

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The electronic transport of monolayer graphene devices is studied before and after in situ deposition of a sub‐monolayer coating of osmium adatoms. Unexpectedly, and unlike all other metallic adatoms studied to date, osmium adatoms shift the charge neutrality point to more positive gate voltages. This indicates that osmium adatoms act as electron acceptors and thus leave the graphene hole‐doped. Analysis of transport data suggest that Os adatoms behave as charged impurity scatterers, albeit with a surprisingly low charge‐doping efficiency. The charge neutrality point of graphene is found to vary non‐monotonically with gate voltage as the sample is warmed to room temperature, suggesting that osmium diffuses on the surface but is not completely removed.

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