Application of Dispersion-Corrected Density Functional Theory

A newly developed dispersion-corrected density functional theory (B3LYP-DCP) was tested against the S22 benchmark set containing noncovalently bound complexes, resulting in a mean absolute deviation of 0.77 kcal mol(-1). It is found that B3LYP-DCP is capable of describing a multitude of weak interactions, including hydrogen bonds. The method was applied to study the toluene dimer, where it is found to describe the dissociation energy (D0 = 3.57 kcal mol(-1)) in excellent agreement with experimental (D0 = 3.46 +/- 0.23 kcal mol(-1)) and recent CCSD(T) counterpoise-corrected (D0 = 3.36 kcal mol(-1)) values. A large number of slipped, stacked isomers are found to be almost isoenergetic. A slipped stack, cross-type isomer is found to be the most stable, and sandwiched and T-shaped dimers appears not to be stationary states on the potential energy surface.