24 March 2000 Ž . Chemical Physics Letters 319 2000 547–554 www.elsevier.nlrlocatercplett Effects of the higher electron correlation correction on the calculated intermolecular interaction energies of benzene and naphthalene dimers: comparison between MP2 and ž / CCSD T calculations Seiji Tsuzuki ) , Tadafumi Uchimaru, Kazunari Matsumura, Masuhiro Mikami, Kazutoshi Tanabe National Institute of Materials and Chemical Research, Tsukuba, Ibaraki, 305-8565, Japan Received 1 May 1999; in final form 22 December 1999 Abstract Intermolecular interaction energies of parallel and T-shape benzene dimers and parallel naphthalene dimer were Ž . Ž . Ž. calculated with MP2, MP3, MP4 SDQ , MP4 SDTQ , CCSD and CCSD T electron correlation corrections using several Ž. basis sets. The MP2 calculations considerably overestimated the attraction compared to the CCSD T ones. The MP2 correlation interaction energies, the differences between the HF and MP2 interaction energies, were 21–38% larger than the Ž. Ž . corresponding CCSD T ones. The MP4 SDQ and CCSD calculations substantially underestimated the attraction compared Ž . Ž. Ž. 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 were y1.74, y2.50 and y5.69 kcalrmol, respectively. q 2000 Elsevier Science B.V. All rights reserved. 1. Introduction Several experimental and theoretical studies have been reported on the nonbonding benzene–benzene w x interaction 1–10 . This interaction is the prototype of p– p interactions between aromatic rings. The interactions between aromatic rings influence three- dimensional structures of protein and DNA and the crystal packing of molecules containing aromatic ) Corresponding author. Fax: q 81-298-614487; e-mail: tsuzuki@nimc.go.jp w x rings 11,12 . The accurate intermolecular interaction potential is strongly requested by those who carry w x out force field simulations of these molecules 13,14 . Although several experimental studies have been w x reported on the benzene–benzene interaction 1–4 , it is still difficult to accurately determine the poten- tial energy surface of benzene dimer only from experimental measurements. The potential energy surface of benzene dimer has been studied by several w x levels of ab initio calculations 5–10 . The dispersion interaction, which has its origin in electron correla- w x tion 15 , is an important interaction for benzene 0009-2614r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0009-2614 00 00170-6