INTERMOLECULAR INTERACTION POTENTIALS OF METHANE AND ETHYLENE DIMERS CALCULATED WITH THE MOLLER-PLESSET, COUPLED-CLUSTER AND DENSITY-FUNCTIONAL METHODS

Intermolecular interaction potentials of methane and ethylene dimers w ere calculated by the Hartree-Fock, Moller-Plesset, coupled cluster an d density functional methods. The CCSD(T) electron correlation energie s were close to the MP4(SDTQ) ones. The MP2 and MP3 energies were not largely different from the MP4(SDTQ) ones. On the other hand the CCSD and MP4(SDQ) methods largely underestimated the electron correlation e nergies. Dispersion interaction was not covered by the density functio nal methods using the BLYP, BPW91 and B3LYP functionals. These functio nals also had defects in the evaluation of the repulsion interactions. (C) 1998 Elsevier Science B.V. All rights reserved.