The physisorption of an acetone molecule on hexagonal graphene nanoflakes with increasing size has been investigated using a variety of quantum chemical methods capable of describing weak intermolecular interactions: coupled-cluster theory (CCSD and CCSD(T)), second-order Møller-Plesset perturbation theory with and without spin-component scaling (SCS-MP2 or standard MP2), long-range corrected density functional theory combined with a van der Waals functional (LC-BOP+ALL), meta-generalized gradient approximation functionals (M06-2X and M05-2X), and the dispersion augmented self-consistent-charge density functional tight-binding (SCC-DFTB-D) method. Our benchmark results for model systems as large as dicircumcoronene C96H24 have confirmed the suitability of the SCS-MP2 method for this specific system and the satisfactory performance of the computationally much more economical semiempirical SCC-DFTB-D method. The latter delivers a qualitatively accurate description of physisorption for flakes containing more than 800 carbon atoms. We predict accurate interaction energies of acetone with an infinitely large, defect-free graphene monolayer by combining extrapolation approaches for both increasing ab initio basis sets and graphene flake size in a two-dimensional extrapolation scheme.
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