Adsorption of Lanthanide Atoms on Graphene: Similar, Yet Different

Abstract

Many theoretical studies address the interaction of different atoms with graphene; however, the relevant information on the adsorption of the lanthanide species remains limited and controversial, creating a gap in this important area of graphene chemistry and physics. By employing periodic density functional theory calculations, we provide the key theoretical information for the entire series from lanthanum to lutetium interacting with defect-free graphene, including the interaction strength and distances, charge and spin of the lanthanide atoms, and comparative features of the density of states. The central lanthanides Gd, Tb, and Dy exhibit the strongest bonding and shortest distances. The positive charge acquired by the lanthanide atoms varies insignificantly, with the exception of Yb and Lu with a filled 4f shell. The spin increases from La to Tb and then decreases sharply, achieving minimal values for Tm, Yb, and Lu. Interaction with graphene influences even the deeper 5s and 5p shells.

Strong Bending Distortion of a Supercoronene Graphene Model upon Adsorption of Lanthanide Atoms

“…While in the periodic calculations 19 the positive charge of most adsorbed Ln species was >1 e (except for Yb and Lu), in the study presented here the only such case is Eu, 1.092 e (Table 1 and the plot in Figure S2). Yb and Lu (0.234 and 0.287 e, respectively) exhibited again the lowest values of all.…”

“…Another possibility is that this phenomenon originates from the existence of a variable number of unpaired 4f electrons. In the latter regard, one should note that in our recent study 19 of Ln atom adsorption on a periodic graphene model (as well as in the previous related studies by other research groups 3,4,10,11,13,14 ), no visible distortion of the planar surface was reported.…”

“…For the sake of comparison, we applied the same PBE-D2/DNP theoretical level with the use of effective core pseudopotentials 39,40 (ECPs) (for the technical details, see the Supporting Information) as in the cluster calculations with Ln 3+ cations, 28 which to a certain degree also matches the periodic planewave-based PBE-D2 methodology. 19 First, compared to both sets of prior results, 19,28 considerable differences can be found in the coordination pattern. Previously, the Ln species was always found to be hexacoordinated (η 6 hapticity), and all Ln 3+ cations were localized over the central hexagonal ring of the supercoronene model.…”

“…Changes in the shortest d Ln•••C distances (smallest values in Table 1) in the Ln+G complexes as a function of (a) the Ln atomic number and (b) the number of unpaired electrons (n ue ) in isolated Ln atoms. (c) Interrelation between the absolute spin values of Ln atoms adsorbed on the supercoronene cluster model (this work) and on the periodic G model 19.…”

“…The systematic theoretical study of the interaction of a broad variety of chemical elements (especially metals) with graphene and graphene-based substrates is an indispensable tool in the search of new efficient approaches for modifying physical, chemical, and other properties of this important class of nanomaterials. − An especially important and intriguing case involves the lanthanide metals (including La itself and the Ce–Lu series) due to their particularly complex 4f electron configurations that can have a strong and nontrivial influence on graphene properties and raise significant challenges in the quantum-chemical treatment. Several density functional theory (DFT) studies have been undertaken with periodic graphene models, but never comprising the full series of 15 elements, ,,− with the only exception being our recent report …”