Benchmark Data for Noncovalent Interactions in HCOOH···Benzene Complexes and Their Use for Validation of Density Functionals.

We present benchmark energetic data for the HCOOH···benzene complexes. The benchmark data were determined by a composite approach based on CCSD(T) calculations. Final binding energies (kcal/mol) are in the range of 1.6-4.8 kcal/mol, and they were used as reference data to test density functionals in the literature. Among the tested local density functionals without empirical dispersion corrections, M06-L is the best performing functional, and M06-L/6-31+G(d,p) gives a mean unsigned error (MUE) of only 0.15 kcal/mol. PBEsol and SOGGA also show promising performance. The best local DFT-D methods are BLYP-D and PBEsol-D, and they give an MUE of 0.15 kcal/mol after removing basis set superposition errors by the counterpoise approach. Empirical dispersion corrections greatly improve the descriptions of noncovalent interactions in HCOOH···benzene dimers. The calculated benchmark data and intermolecular potential are useful for the parametrizations of new force fields and coarse-grained models for chemical species such as the acrylic polymers.