OXYGEN ISOTOPE EXCHANGE KINETICS BETWEEN H2O AND H4SIO4 FROM AB INITIO CALCULATIONS
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dc.contributor.author | Felipe M.A. | |
dc.contributor.author | Kubicki J.D. | |
dc.contributor.author | Rye D.M. | |
dc.date.accessioned | 2022-03-23T07:44:06Z | |
dc.date.available | 2022-03-23T07:44:06Z | |
dc.date.issued | 2004 | |
dc.identifier | https://www.elibrary.ru/item.asp?id=12090658 | |
dc.identifier.citation | Geochimica et Cosmochimica Acta, 2004, 68, 5, 949-958 | |
dc.identifier.issn | 0016-7037 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/36569 | |
dc.description.abstract | Oxygen isotope exchange between H2O and H4SiO4 was modeled with ab initio calculations on H4SiO4 + 7H2O. Constrained optimizations were performed with the B3LYP/6–31+G(d,p) method to determine reactants, transition states, and intermediates. Long-range solvation was accounted for using self-consistent reaction field calculations. The mechanism for exchange involves two steps, a concerted proton transfer from H4SiO4 forming a 5-coordinated Si followed by a concerted proton transfer from the 5-coordinated Si forming another H4SiO4. The 5-coordinated Si intermediate is C2 symmetric. At 298K and with implicit solvation included, the Gibbs free energy of activation from transition state theory is 66 kJ/mol and the predicted rate constant is 16 s−1. Equilibrium calculations between 298K and 673K yield αH4SiO4-H2O that are uniformly less than, but similar to, αqtz-H2O, and therefore αqtz-H4SiO4 is expected to be relatively small in this temperature range. | |
dc.title | OXYGEN ISOTOPE EXCHANGE KINETICS BETWEEN H2O AND H4SIO4 FROM AB INITIO CALCULATIONS | |
dc.type | Статья |
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