A refined evaluation of the gas-phase water-dimerization equilibrium constant within non-rigid BJH- and MCY-type potentials |
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Authors: | Z. Slanina J. -F. Crifo |
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Affiliation: | (1) Max-Planck-Institut für Chemie (Otto-Hahn-Institut), W-6500 Mainz, Germany;(2) Present address: The J. Heyrovský Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, Dolejkova 3, CS-18223 Prague 8-Kobylisy, Czech and Slovak Federal Republic;(3) Institut d'Astrophysique Spatiale, Centre National de la Recherche Scientifique, B.P. 10, F-91371 Verrières Le Buisson Cedex, France |
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Abstract: | The flexible BJH- and flexible or semiflexible MCY-type water-water potentials (4 potential modifications in each nonrigid family, i.e., altogether 12 potentials) are used for evaluation of the gas-phase water-dimerization equilibrium constants. The potential-energy term is adjusted for best reproduction of the available experimental equilibrium constants. An independent test using the experimental steam second-virial coefficient isotopic difference shows that the adjustment also improves the computational evaluation of the difference. A set of dimerization equilibrium constants is suggested over a wide temperature interval (based on the BJH/G, MCY-B, or MCYB potential modifications). The best reproduction of the experimental equilibrium constants (in conjunction with good performance for the second-virial isotopic difference) is produced by the BJH/G potential. The results are applicable to various problems such as the formation of water clusters in large-scale natural and artificial water jets (e.g., hydrogen-oxygen rocket motors, orbital capsule water dumps, water ejection from a comet nucleus) or in atmospheric chemistry. |
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Keywords: | clustering cometary or planetary atmospheres steam water-dimerization equilibrium constant water-dimer populations |
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