Transition Metal Adatoms on Pristine Graphene

Here we discuss some representative examples in the modeling of transition metal adatoms on pristine graphene. Depending on the system, pristine graphene can be considered as a substrate or ligand for transition metals. The binding of defective graphene to transition metals is of a different nature and the topic is discussed in Section 11.3.3. 

Hobza and coworkers performed a comparative study of Ag, Au, and Pd atoms binding to graphene [114] with electron correlation (CCSD(T) and MP2 with Douglas-Kroll Hamiltonians), conventional (i.e., LDA and GGA) and dispersionaccounting DFT methods (PBE-D3, M06-2X, vdW-DF, and EE -I- vdW). Binding of these metals to graphene is of varied nature, but it is due to electron correlation, as ROHF/ANO-RCC-VTZP benzene-metal potential energy curves have no minima. 

Pd was found to form a covalent T -bond [114] with the graphene sheet. PBE considerably overestimates (-27.3kcalmoH ) as compared to DK-CCSD(T)/ANO-RCC-VTZP in the benchmark on benzene (—19.7kcalmol ). However, in this study only valence-shell electrons were correlated, so it should 

The energy of Co atom binding to graphene sheet predicted with GGA-PW91 is more than five times lower than that to the coronene molecule predicted by CASSCF (complete active space self-consistent field) with a complex basis set of triple- quality (Table 11.3, rows 8 and 9). Such a severe discrepancy is surprising even considering the different graphene models used. This also may be caused by the incompleteness of active space in the CASSCF calculations as only it-orbitals of coronene and d-orbitals of Co were included. 

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