Small Basis Set Allowing the Recovery of Dispersion Interactions with Double-Hybrid Functionals.

Taking advantage of the compensation between Basis Set Superposition Error and Basis Set Incompleteness Error, a new basis is developed to improve the performances of Double Hybrid (DH) functionals in reproducing interaction energies in weak noncovalent systems. Using a self-consistent formula, containing only energy terms computed for dimers and the corresponding monomers at the same level of theory, the exponents of the more external functions of the Def2-SVPD basis were optimized on three systems extracted from the S22 set. The transferability of the obtained basis set, called DH-SVPD, was then tested on five benchmark sets, and it is assessed by considering six DH functionals, eventually corrected with empirical dispersion corrections (for a total of 16 methods). Our results show that this simple approach is able to provide accurate results for noncovalent interaction energies of all the considered systems, and, in particular, to recover the performances obtained by coupling the DH functionals with empirical dispersion corrections.