Orbital Interactions between a C₆₀ Molecule and Cu(111) Surface

Abstract

C−Cu orbital interactions between a two-layer Cu10 or three-layer Cu34 cluster model of a Cu(111) surface and an adsorbed single C60 molecule have been theoretically investigated, so as to elucidate the nature of the C60−Cu(111) bonding and orientational configuration of the C60 molecule on a Cu surface. Geometry optimizations and single-point calculations at the B3LYP/LanL2MB level of theory and fragment molecular orbital (FMO) analyses, coupled with a paired-interaction-orbital (PIO) scheme at the extended Hückel level of theory, have been performed for five symmetric adsorption models, in which a C60 molecule is attached to the Cu10 or Cu34 cluster respectively by a six-membered ring (6-ring), by a five-membered ring (5-ring), by a C−C bond belonging to two 6-rings (6−6 bond), by a C−C bond belonging to a 6-ring and a 5-ring (5−6 bond), and by an edge carbon atom that is located at the center of two 6-rings and a 5-ring. Large stabilization is obtained for adsorption by an edge carbon atom or a 6−6 bond, whereas the other coordination types are not favored. Our result differs from an XPD experimental result for a C60 monolayer on Cu(111), in which adsorption by a 6-ring is most favored. The discrepancy strongly suggests that C60−C60 interactions contribute significantly to the determination of C60 orientations in C60/Cu(111) monolayer systems.

Doping-induced reorientation ofC60molecules on Ag(111)

“…For example, calculations on single C 60 molecules adsorbed on metal surfaces, where the hybridization between the C 60 molecules is absent, show another orientation than experiments performed on full layers. 22 The relative importance of the different interactions can be estimated from a comparison with bulk C 60 . Since the orientations found in the monolayer are close to the ones known for the bulk systems, it seems that the molecule-molecule and the moleculeion interactions are the dominant effects that determine the relative orientation in the layer.…”

Orientation of individualC60molecules adsorbed on Cu(111): Low-temperature scanning tunneling microscopy and density functional calculations

“…For instance, some of the binding configurations reported in Ref. 25 are not plausible, possibly because they used a smaller metal cluster model of the surface and restricted the positions of the metal atoms to be at bulk positions, which has been shown to be a severe approximation since lengthening of the Cuu Cu bonds at the surface has been found for C 60 bound to Cu͑111͒. 48 However, they do cast doubt on the XPD results in Ref.…”

“…They also studied the rotational orientation of C 60 on each of these binding sites. The theoretical study of Ogawa et al 25 using DFT with a generalized gradient approximation ͑GGA͒ hybrid functional considered bonding of several polar angles and azimuthal orientations of the C 60 molecule relative to the on-top site of Cu͑111͒ and found the most stable to be a polar angle orientation with a C -C partial double bond between two six-membered rings ͑a six-six bond͒ directed toward the surface. However, the binding energies for all configurations considered in their study, including a configuration with a six-membered ring oriented toward the surface, were within 500 meV of one another.…”

Vacancy patterning and patterning vacancies: controlled self-assembly of fullerenes on metal surfaces

“…16 The adsorption of C 60 on metal surfaces is indeed a topic that has drawn much attention over the last years, and the nature of the C 60 4 substrate chemical bonding is still a matter of debate. Related research has involved a variety of transition metals (Au, [17][18][19][20][21][22][23] Ag, [24][25][26] Ni, 27,28 Pd, 29 Pt, [30][31][32][33][34] and Cu [35][36][37][38][39][40] ) and even few p-group metals (Al [41][42][43][44] and Si 45,46 ), combining experiments and theoretical calculations. The latter mostly rely on Density Functional Theory (DFT), although for such systems the inclusion of a proper description of van der Waals (vdW) dispersive forces appears mandatory.…”