title: I + (H2O)2 → HI + (H2O)OH Forward and Reverse Reactions. CCSD(T) Studies Including Spin-Orbit Coupling.
abstract: The potential energy profile for the atomic iodine plus water dimer reaction I + (H2O)2 → HI + (H2O)OH has been explored using the "Gold Standard" CCSD(T) method with quadruple-ζ correlation-consistent basis sets. The corresponding information for the reverse reaction HI + (H2O)OH → I + (H2O)2 is also derived. Both zero-point vibrational energies (ZPVEs) and spin-orbit (SO) coupling are considered, and these notably alter the classical energetics. On the basis of the CCSD(T)/cc-pVQZ-PP results, including ZPVE and SO coupling, the forward reaction is found to be endothermic by 47.4 kcal/mol, implying a significant exothermicity for the reverse reaction. The entrance complex I···(H2O)2 is bound by 1.8 kcal/mol, and this dissociation energy is significantly affected by SO coupling. The reaction barrier lies 45.1 kcal/mol higher than the reactants. The exit complex HI···(H2O)OH is bound by 3.0 kcal/mol relative to the asymptotic limit. At every level of theory, the reverse reaction HI + (H2O)OH → I + (H2O)2 proceeds without a barrier. Compared with the analogous water monomer reaction I + H2O → HI + OH, the additional water molecule reduces the relative energies of the entrance stationary point, transition state, and exit complex by 3-5 kcal/mol. The I + (H2O)2 reaction is related to the valence isoelectronic bromine and chlorine reactions but is distinctly different from the F + (H2O)2 system.
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.affiliation: Center for Computational Quantum Chemistry, University of Georgia , Athens, Georgia 30602, United States.
authors.forename: Guoliang
authors.initials: G
authors.lastname: Li
authors.forename: Qian-Shu
authors.initials: QS
authors.lastname: Li
authors.affiliation: Center for Computational Quantum Chemistry, University of Georgia , Athens, Georgia 30602, United States.
authors.forename: Yaoming
authors.initials: Y
authors.lastname: Xie
authors.affiliation: Center for Computational Quantum Chemistry, University of Georgia , Athens, Georgia 30602, United States.
authors.forename: Henry F
authors.initials: HF
authors.lastname: Schaefer