Graphene on Ni(111): Strong interaction and weak adsorption

The adsorption of graphene on Ni(111) has been investigated on the basis of the adiabatic-connection fluctuation-dissipation theorem in the random phase approximation (RPA). Although we find a significant hybridization between the graphene $\pi$ orbitals and Ni $d_{z^2}$ states at a binding distance of 2.17 Å, the adsorption energy is still in the range of a typical physisorption (67 meV per carbon). An important contribution to the energy is related to a decrease in the exchange energy resulting from the adsorption-induced lower symmetry in the graphene layer. The energetics can be well reproduced using the computationally significantly cheaper van der Waals density functional theory with an appropriately chosen exchange-correlation functional.

Figure 1

Graphene adsorption on Ni(111) in a top-fcc (a) and top-hcp (b) configuration. (c) DFT adsorption energies vs distance $d$ calculated with the LDA (red and pink lines) and the PBE exchange-correlation functional (green and blue lines).

Figure 2

(a) DFT (PBE) band structure of graphene/Ni(111) at a distance of 2.1 and 3 Å projected at the carbon atoms. (b) Differential charge induced by the adsorption of graphene on Ni(111) for a distance of 2.1 Å: The blue/dark gray (red/light gray) areas mark an increase (decrease) of the charge density. No significant changes in the differential charge distribution can be observed at a distance above 3 Å.

Figure 3

RPA adsorption energies for the adsorption of graphene on Ni(111) in the top-fcc (red/gray line) and top-hcp (inset) configuration. The total adsorption energy is separated into the exchange (blue/dark gray line) and correlation contributions (green/medium gray line). The pink/light gray line indicates an analytic fit to the long-range correlation contributions.

Figure 4

Adsorption of graphene (top fcc) on Ni(111) using the vdW DFT as a function of the exchange-correlation functional.