Coupled cluster and density functional investigation of the neutral sodium-benzene and potassium-benzene complexes

By means of coupled-cluster calculations we studied the neutral complexes: Na-benzene and K-benzene. They are non-ionic presenting C-6v symmetry. In contrast with the results obtained for Li-benzene, the non-ionic C-2v structure was not a minimum. At the CCSD(T)/CBS level of theory, with the inclusion of relativistic and core-valence effects, the dissociation energies for sodium and potassium benzene complexes are 2.4 and 3.3 kcal/mol, respectively. We found that most density functionals overestimate the adsorption energies of alkalis onto benzene. Therefore, special caution must be taken when DFT methods are employed to investigate the interactions between these elements and carbon nanomaterials. (C) 2018 Elsevier B. V. All rights reserved.