Bridge structure for the graphene/Ni(111) system: A first principles study

The structure of graphene on Ni(111) is studied with density functional theory (DFT). Six different structures, i.e., top-fcc, top-hcp, hcp-fcc, bridge-top, bridge-fcc, and bridge-hcp, were investigated. Bridge-top, bridge-fcc, and bridge-hcp are studied here. Top-fcc and hcp-fcc have been considered before, experimentally and theoretically, and regarded as energetically stable structures. The calculations employed the local density approximation (LDA) and the Perdew, Burke, and Ernzerhof (PBE) generalized-gradient approximation to DFT. The results showed that with PBE, none of the structures is stable at the experimentally relevant temperatures; with LDA, only bridge-top and top-fcc are stable. These findings suggest that it will be worthwhile to carry on new experimental studies to revisit the structural determination of the graphene/Ni(111) system, with special emphasis on testing whether bridge-top could exist by itself or coexist with other structures.

Figure 1

(Color online) Structures considered so far for graphene over the Ni(111) surface seen from above (top) and from the side (bottom). (a) top-hcp, (b) top-fcc, and (c) hcp-fcc. Color code: Ni, green, yellow, red, and blue; C, black. Ni in the first (top), second (hcp), and third (fcc) layers are shown in green, yellow, and red, respectively. The arrows define the parameters $d_0$, $d_1$, and $d_2$, see Table . The dashed lines are used as a visual aid to show how a C atom is placed with respect to a Ni atom.

Figure 2

(Color online) Bridge structures of graphene over the Ni(111) surface seen from above (top) and from the side (bottom). (a) bridge-top, (b) bridge-hcp, and (c) bridge-fcc. Color code: Ni, green, yellow, red, and blue; C, black. Ni in the first (top), second (hcp), and third (fcc) layers are shown in green, yellow, and red, respectively. The dashed lines are used as a visual aid to show how a C1-C2 bond is placed with respect to a Ni atom.