Effects of the higher electron correlation correction on the calculated intermolecular interaction energies of benzene and naphthalene dimers: comparison between MP2 and CCSD(T) calculations

Intermolecular interaction energies of parallel and T-shape benzene dimers and parallel naphthalene dimer were calculated with MP2, MP3, MP4(SDQ), MP4 (SDTQ), CCSD and CCSD(T) electron correlation corrections using several bas is sets. The MP2 calculations considerably overestimated the attraction com pared to the CCSD(T) ones. The MP2 correlation interaction energies, the di fferences between the HF and MP2 interaction energies, were 21-38% larger t han the corresponding CCSD(T) ones. The MP4(SDQ) and CCSD calculations subs tantially underestimated the attraction compared to MP4(SDTQ) and CCSD(T), which indicated the importance of triple excitation. The estimated CCSD(T) interaction energies of the three dimers with reasonably large basis sets w ere - 1.74, - 2.50 and - 5.69 kcal/mol, respectively. (C) 2000 Elsevier Sci ence B.V. All rights reserved.