Exploring the limits of recent exchange-correlation functionals in modeling lithium/benzene interaction

The interaction of the lithium alkaline metal, with the benzene molecule, is herein investigated in the framework of density functional theory (DFT) method. Performances of a large set of exchange-correlation functionals in reproducing some physical properties are benchmarked using as reference the CCSD(T) method at the complete basis set limit (CCSD(T)/CBS). Both the cationic and neutral lithium-benzene systems (LiBz(+) and LiBz) are considered as well as the sandwich compound (BzLiBz(+)). Among all the functionals, omega B97X emerges as the best approach for modeling all the three systems analyzed, while large deviations are observed for several functionals in the case of the problematic neutral Li-benzene system. Particular attention was devoted to the discussion of the results obtained with methods containing empirical dispersion corrections. More broadly, our results underline the difficulties and the limits of current DFT approaches in the description of the interaction of Li with aromatic molecules, which is relevant in several applied fields.