Non-covalent interactions and thermochemistry using XDM-corrected hybrid and range-separated hybrid density functionals

The exchange-hole dipole-moment model (XDM) for dispersion is combined with a collection of semilocal, hybrid, and range-separated hybrid functionals. The resulting XDM-corrected functionals are tested against standard benchmarks for non-covalent interactions at and away from equilibrium, conformer ranking in water clusters, thermochemistry, and kinetics. We show that functionals with the correct -1/r tail of the exchange potential yield superior accuracy for weak interactions. Thus, balancing long-range exchange with dispersion interactions in XDM is essential in the correct description of dimers with significant non-dispersion contributions to binding. With the exception of the noble gases, the performance of PW86PBE-XDM is improved upon at the semilocal (BLYP), hybrid (B3LYP), and range-separated hybrid (LC-omega PBE) levels. Based on its excellent performance, we propose LC-omega PBE-XDM as an accurate functional for hard and soft matter. (C) 2013 AIP Publishing LLC.