Accurate calculations of the noncovalent systems with flat potential energy surfaces: Naphthalene dimer and azulene dimer

Abstract

It is very challenging to construct the potential energy surfaces for the medium and large noncovalent systems employing the coupled clusters with singles, doubles, and perturbative triples, CCSD(T), at the complete basis set (CBS) limit. The main obstacle lies in the time-consuming and expensive CCSD(T) optimizations of the geometries. One method to overcome the obstacle is to use the cheap density functional theory with the D3 dispersion correction (DFT-D3) instead of the CCSD(T) method to optimize the geometries of the noncovalent systems. In the present study, the potential energy surfaces of the naphthalene dimer and azulene dimer were investigated using a combined DFT-D3 optimization and single-point CCSD(T)/CBS energy calculation scheme. The results clearly show that this scheme can give highly accurate CCSD(T)/CBS potential energy surfaces for the naphthalene dimer and the azulene dimer.