title: Theoretical Study on the Structure and the Frequency of Isomers of the Naphthalene Dimer.
abstract: The structures of the naphthalene monomer and dimer were investigated with performing vibrational analysis. The MP2 optimization showed that the naphthalene monomer has a nonplanar geometry in the 6-31G, 6-31G*, 6-31+G*, and 6-311G basis sets, while it has a planar geometry in the 6-31G*(0.25) and Dunning's correlation consistent basis sets. The MP2/cc-pVDZ calculation showed the presence of the four stable isomers, which were part of the isomers in the previous MP2/6-31G* calculation (Walsh, T. R. Chem. Phys. Lett. 2002, 363, 45). The presence of extra structures in the MP2/6-31G* calculation is attributed to a poor description of the potential energy surface, which is evident from the nonplanar structure of the monomer in the MP2/6-31G* calculation. The relative stability among the isomers in the MP2/cc-pVDZ calculation without counterpoise correction was maintained in both the single-point calculation at the MP2/aug-cc-pVDZ//MP2/cc-pVDZ level and the counterpoise-corrected optimization at the MP2/cc-pVDZ level. The relative stability among the isomers suggested an enhancement of the π-π interaction in the structure with lower symmetry, which could be explained using a molecular-orbital model. The vibrational analysis in MP2/cc-pVDZ without the counterpoise correction suggested that the isomers of the naphthalene dimer were distinguishable by the observation of the infrared spectrum in the low-frequency region (150-600 cm(-)(1)).
authors.affiliation: Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.|Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Morihisa
authors.initials: M
authors.lastname: Saeki
authors.affiliation: Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.|Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Akagi
authors.affiliation: Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.|Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Fujii