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1 Polish Journal of Chemistry

1 1998

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The influence of the O-H stretch and O...O distance on the many-body interactions in the cyclic water trimer

Rak J., Szczęśniak M.M., Chałasiński G., Cybulski S.M.

Polish Journal of Chemistry

1998

Vol. 72, nr 7S

1505-1523

The effects of the O-H stretch and changes in the O...O distance upon the one-, two- and three-body interaction energy components were studied in a cyclic water trimer. Calculations were carried out using supermolecular Moller-Plesset perturbation (S-MPPT) theory in conjunction with perturbation theory of intermolecular forces, also known as intermolecular Moller-Plesset theory (I-MPPT). The dependence of the one-body relaxation as well as electrostatic, induction, exchange and dispersion terms upon changes in the intramolecular O-H bond length and upon the intermolecular O...O distance were studied to identify the terms which have the strongest influence on the structural parameters of the trimer. We found that the one-body terms must be evaluated at a high level of theory (MP4) with an elaborate basis set. The two-body perturbation energies appear to be reliably reproduced through the second order (MP2), and the three-body terms are reliable already at the self consistent field (SCF) level of theory. The two-body and three-body terms vary approximately linearly with the OH stretch of proton-donors.