Interaction Energy of Large Molecules from Restrained Denominator MP2-F12

A new one-parameter correction scheme to second-order Moller-Plesset many-body perturbation theory (MP2) has been proposed to correctly evaluate intermolecular interaction energies of large pi-pi dispersion interaction systems as well as hydrogen-bonded and ss dispersion interaction ones. The scheme restrains the denominator of the MP2 correlation energy expression based on the observation that larger corrections to MP2 are required as the orbital energy gaps become small as in large pi-pi stacking systems. The root-mean-square-deviation of the restrained denominator MP2 with F12 correction (RD-MP2-F12) on the S66 set of 0.346 kcal/mol is less than half of that of MP2-F12. The interaction energies of RD-MP2 are similar to those of dispersion corrected density functional theory for a series of polyaromatic hydrocarbon dimers. For the C-60-fullerene dimer, however, the RD-MP2-F12 result somewhat deviates from the experimental estimate, indicating that an explicit inclusion of higher order correlation is required for the system.