Application of 25 density functionals to dispersion-bound homomolecular dimers

The ability of 25 density functional theory (DFT) methods to treat Ne2, Ar2, (CH4)2, (C2H4)2 and three conformations of the benzene dimer was studied. Only PW91, HTCH407, and VSXC predict all dimers to be bound. However, VSXC strongly over-binds all of the complexes. The DFTs predict repulsive potential energy surfaces (PES) for parallel benzene at large separations, in contrast to MP2. VSXC, B1B95, BB95, and BB1K, and to a lesser extent OLYP and O3LYP, are sensitive to the size of the integration grid used. When used with standard grids, these methods predict multiple minima on one or more dimer PESs.