Benchmark calculations of water-acene interaction energies: Extrapolation to the water-graphene limit and assessment of dispersion-corrected DFT methods

In a previous study (J. Phys. Chem. C, 2009, 113, 10242-10248) we used density functional theory based symmetry-adapted perturbation theory (DFT-SAPT) calculations of water interacting with benzene (C6H6), coronene (C24H12), and circumcoronene (C54H18) to estimate the interaction energy between a water molecule and a graphene sheet. The present study extends this earlier work by use of a more realistic geometry with the water molecule oriented perpendicular to the acene with both hydrogen atoms pointing down. We also include results for an intermediate C48H18 acene. Extrapolation of the water-acene results gives a value of -3.0 +/- 0.15 kcal mol(-1) for the binding of a water molecule to graphene. Several popular dispersion-corrected DFT methods are applied to the water-acene systems and the resulting interacting energies are compared to results of the DFT-SAPT calculations in order to assess their performance.