A comparative electron correlation treatment in H(2)S-benzene dimer with DFT and wavefunction-based ab initio methods.

Three major conformations of H(2)S-benzene dimer have been located with a variety of density functional theories (DFT) and second order Møller-Plesset perturbation (MP2). In line with an experiment, MP2 results indicate that the tilted C(s)-symmetry structure is a stable dimer, yet a C(2v)-symmetry structure is only a second-order saddle point. Although all of the examined DFT methods also predict the binding between H(2)S and benzene as MP2 and the coupled cluster method with single and double excitations and perturbative triples (CCSD(T)) do, they considerably underestimate binding energies as compared with CCSD(T) results. However, PW91LYP and MPWB1K reproduce the binding sequence obtained with MP2 for the dimers, and provide the best binding energies among the tested DFT methods. The method of increments with the orbitals of H(2)S and π orbitals of the benzene recovers 99% of the total binding from the full CCSD(T).